Infinite loading or streaming when joining P2P multiplayer server
Since July 1st me and 3 friends have been unable to successfully load each other's multiplayer worlds. We can join the session but are repeatedly trapped at either 50% or 100% loaded until the game is force exited. If we do load in, we can get as far as the respawn screen and can see the possible spawn locations, however choosing to respawn at one will result in an infinitely rotating streaming icon. The host can see the players spawning in T-pose but they never have control of the characters. If these players leave and successfully rejoin they see a completely empty void, no textures or models. Single player worlds and official servers work normally for everyone. We all run the game through Steam.
We have all tried:
- disabling all mods
- loading previously working copies of our world
- loading a vanilla default world(red platform & star system)
- deleting the space_engineers.cfg files
- deleting the shader cache folder
- verifying integrity of game files
- fully deleting and reinstalling the game, including deleting all files/folders missed by steam uninstall
- 3 different players hosting in 2 different steam download regions
- all players restarting steam and space engineers in every order and configuration possible
- updating all drivers
- probably a couple other things that I'm forgetting
The issue did not happen all at once. One friend had the issue, while the other 2 could join. After restarting Steam, the second player was unable to join. A month later(the next time we tested) the third player could not join.
It really looks like you have some sort of issue with Steam peer to peer connections that popped up around the start of July, you'll see several other reports on Reddit around then of exactly this issue. I attached the log files for myself(HappyMonk3y99) and my friend Sargent_X which show both the host and client side logs. We have a 3 hour time difference so you'll see the overlap around 23:22:XX for Sargent_X and 20:22:XX for me.
If you have any more ideas for troubleshooting I'd be happy to try but I think this is on your/Steam's end.
I have the same bug
Hello!
Thank you for contacting us. Since this is a bug report, I'm moving your ticket to our support page, where our QA team will take care of you.
Kind Regards
Keen Software House
Hello!
Thank you for contacting us. Since this is a bug report, I'm moving your ticket to our support page, where our QA team will take care of you.
Kind Regards
Keen Software House
Are there any updates on this?
Are there any updates on this?
Hello Mike,
Thank you very much for providing the logs, they’ve been extremely helpful.
From both the host and client files, we can confirm that the world transfer is completing successfully and the session is being created correctly. The issue occurs afterward, during the peer-to-peer synchronization stage.
This behavior seems to be from the Steam networking side, which sometimes lead to stalled “streaming” states or T-pose spawns in P2P sessions, even though the game itself is functioning correctly.
To move forward, could you please check the following and try these steps?
Questions (for all players in the session):
(Steam → Settings → Downloads → Download Region)
Recommended Workarounds
For the Host (and ideally the clients as well):
Add this launch option in Steam → Library → Right-click Space Engineers → Properties → Launch Options:
-nothreadedsteamapi
This forces the game to use the legacy Steam API, which often bypasses the P2P sync issue.
For all players (host + clients):
Add this additional launch option:
-steamdatagram_transport_udp 2
This routes P2P traffic through Steam’s relay servers, which could resolve the infinite streaming problem.
Please ensure that all players restart Steam after applying the launch options.
Once you’ve tried this configuration, let us know if the connection behavior changes (even partially).
Thanks again for your patience.
Kind Regards,
Keen Software House: QA Department
Hello Mike,
Thank you very much for providing the logs, they’ve been extremely helpful.
From both the host and client files, we can confirm that the world transfer is completing successfully and the session is being created correctly. The issue occurs afterward, during the peer-to-peer synchronization stage.
This behavior seems to be from the Steam networking side, which sometimes lead to stalled “streaming” states or T-pose spawns in P2P sessions, even though the game itself is functioning correctly.
To move forward, could you please check the following and try these steps?
Questions (for all players in the session):
(Steam → Settings → Downloads → Download Region)
Recommended Workarounds
For the Host (and ideally the clients as well):
Add this launch option in Steam → Library → Right-click Space Engineers → Properties → Launch Options:
-nothreadedsteamapi
This forces the game to use the legacy Steam API, which often bypasses the P2P sync issue.
For all players (host + clients):
Add this additional launch option:
-steamdatagram_transport_udp 2
This routes P2P traffic through Steam’s relay servers, which could resolve the infinite streaming problem.
Please ensure that all players restart Steam after applying the launch options.
Once you’ve tried this configuration, let us know if the connection behavior changes (even partially).
Thanks again for your patience.
Kind Regards,
Keen Software House: QA Department
Questions (for all players in the session):
Everyone is using their own copy without steam family sharing.
(Steam → Settings → Downloads → Download Region)
No, of 5 people, we were using 3 download regions. 3 people were in the same region, 1 each in 2 other regions.
No
Workaround Results(TLDR: No change from adding these CLI flags) - Skip to end for the workaround we found
Add this launch option in Steam → Library → Right-click Space Engineers → Properties → Launch Options:
-nothreadedsteamapi
Download regions used for testing: Initial host - San Jose, CA; Initial Client - Boston, MA
Results on a friends only world on default Star System, 'continue game' used to reload server between attempts:
Change made by host only -> Issue persists with no change. Client loads to 100% but never joins.
Change made by host and client -> Issue persists with no change. Client loads to 100% but never joins.
Host and client switch roles, all settings the same:
Change made by host only -> Same result
Change made by host and client -> Same result
Host and client disable all launch options -> Same result
For all players (host + clients):
Add this additional launch option:
-steamdatagram_transport_udp 2
Results on Friends only world on default Star System, 'continue game' used to reload server between attempts:
Change made by host and client -> Issue persists with no change. Client loads to 100% but never joins.
Client matches download region to host's(San Jose, CA) -> Same result
Host and client switch roles, all settings the same:
Change made by host and client -> Same result
However we did find a workaround:
The server had not been appearing on the in game server browser. This was consistent across all tests so we were attempting to join through the steam overlay. Changing all of our download regions to San Jose, CA to match the host allows us to see the server in the in game server browser. Then joining through that browser allowed all players to successfully load the world(No command line flags needed). Attempting to join through Steam in any way fails and results in an infinite load attempt. World privacy does not matter, all types can be used as long as the in game server browser is used to join.
Questions (for all players in the session):
Everyone is using their own copy without steam family sharing.
(Steam → Settings → Downloads → Download Region)
No, of 5 people, we were using 3 download regions. 3 people were in the same region, 1 each in 2 other regions.
No
Workaround Results(TLDR: No change from adding these CLI flags) - Skip to end for the workaround we found
Add this launch option in Steam → Library → Right-click Space Engineers → Properties → Launch Options:
-nothreadedsteamapi
Download regions used for testing: Initial host - San Jose, CA; Initial Client - Boston, MA
Results on a friends only world on default Star System, 'continue game' used to reload server between attempts:
Change made by host only -> Issue persists with no change. Client loads to 100% but never joins.
Change made by host and client -> Issue persists with no change. Client loads to 100% but never joins.
Host and client switch roles, all settings the same:
Change made by host only -> Same result
Change made by host and client -> Same result
Host and client disable all launch options -> Same result
For all players (host + clients):
Add this additional launch option:
-steamdatagram_transport_udp 2
Results on Friends only world on default Star System, 'continue game' used to reload server between attempts:
Change made by host and client -> Issue persists with no change. Client loads to 100% but never joins.
Client matches download region to host's(San Jose, CA) -> Same result
Host and client switch roles, all settings the same:
Change made by host and client -> Same result
However we did find a workaround:
The server had not been appearing on the in game server browser. This was consistent across all tests so we were attempting to join through the steam overlay. Changing all of our download regions to San Jose, CA to match the host allows us to see the server in the in game server browser. Then joining through that browser allowed all players to successfully load the world(No command line flags needed). Attempting to join through Steam in any way fails and results in an infinite load attempt. World privacy does not matter, all types can be used as long as the in game server browser is used to join.
Hello Mike,
Thank you for the detailed follow-up and for testing all the steps so thoroughly.
We’re glad to hear that you were able to join successfully. And, joining through the in-game server browser instead of the Steam overlay strongly suggests the issue lies on the Steam networking side.
Could you please confirm if this workaround remains reliable after restarting Steam and rejoining multiple times?
Thank you again for your patience and cooperation.
Kind Regards,
Keen Software House: QA Department
Hello Mike,
Thank you for the detailed follow-up and for testing all the steps so thoroughly.
We’re glad to hear that you were able to join successfully. And, joining through the in-game server browser instead of the Steam overlay strongly suggests the issue lies on the Steam networking side.
Could you please confirm if this workaround remains reliable after restarting Steam and rejoining multiple times?
Thank you again for your patience and cooperation.
Kind Regards,
Keen Software House: QA Department
Hello Mike,
We’ve reproduced the issue and created an internal ticket for further investigation.
The workaround you suggested will definitely be helpful to other players in the meantime, and we appreciate you sharing it.
Kind Regards,
Keen Software House: QA Department
Hello Mike,
We’ve reproduced the issue and created an internal ticket for further investigation.
The workaround you suggested will definitely be helpful to other players in the meantime, and we appreciate you sharing it.
Kind Regards,
Keen Software House: QA Department
I haven't had a chance to test again yet, however it was very consistent at the time testing with multiple players joining and with different players hosting. I'll follow up again when I have time. Happy to hear you were able to reproduce the issue, looking forward to a fix!
I haven't had a chance to test again yet, however it was very consistent at the time testing with multiple players joining and with different players hosting. I'll follow up again when I have time. Happy to hear you were able to reproduce the issue, looking forward to a fix!
Hello!
Thank you for contacting us. Since this is a bug report, I'm moving your ticket to our support page, where our QA team will take care of you.
Kind Regards
Keen Software House
Hello!
Thank you for contacting us. Since this is a bug report, I'm moving your ticket to our support page, where our QA team will take care of you.
Kind Regards
Keen Software House
Hello Sawely,
Thank you for reaching out to us on the forum.
The issue is related to joining via the Steam Overlay. We are already aware of this issue, and there is an internal ticket open for it here:
https://support.keenswh.com/spaceengineers/pc/topic/48996
Since the issue is still under investigation internally, please try the following workarounds in the meantime, as they may help;
Once done, the host’s game should appear in the Join Game > Friends screen for all clients. Please check if you can then successfully join this way.
Since this issue is the same as the one mentioned in the above thread, we are merging this thread with that one for now.
Thank you for your understanding.
Kind regards,
Keen Software House: QA Department
Hello Sawely,
Thank you for reaching out to us on the forum.
The issue is related to joining via the Steam Overlay. We are already aware of this issue, and there is an internal ticket open for it here:
https://support.keenswh.com/spaceengineers/pc/topic/48996
Since the issue is still under investigation internally, please try the following workarounds in the meantime, as they may help;
Once done, the host’s game should appear in the Join Game > Friends screen for all clients. Please check if you can then successfully join this way.
Since this issue is the same as the one mentioned in the above thread, we are merging this thread with that one for now.
Thank you for your understanding.
Kind regards,
Keen Software House: QA Department
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