10-30 second sync delays

I've been playing multiplayer on a pingperfect hosted DS for a few days now, and have been continually having a problem best described as "sync delays".

The game will be working fine. I can build, weld, etc, then all of a sudden, one time I try to build, this will happen:

1. I'll click to build the light armor I'm holding to add it to a grid (in survival)
2. I'll hear the placement sound effect
3. The block will not appear on my screen
4. My inventory has been reduced by the cost of the block
5. The other person I'm playing will tell me over voice chat that he sees the block
6. If I try to move where the block is, the client prediction (which doesn't know the block is there) will let me, for a moment, before it rubber-bands me back.
7. Something like 10-30 seconds after having placed the block, I will hear the placement sound effect again, and the block will show up.

After the first block fails to show up, if I build more blocks elsewhere, then 10-30 seconds later then all show up rapidly in succession.

A similar thing happens with welding and grinding. For example:

1. I'll be welding a series of blocks, working fine
2. Suddenly one block will stop welding
3. My % progress meter stops going up
4. I never see the block graphics change to the "finished" block
5. My inventory is reduced by the cost of welding the block
6. The other player in the game can see that the block is finished.
7. 10-30 seconds later, I'll hear a sound effect, and the block will finish.

Again, if I weld multiple blocks when this is happening, I can't see anything happening, but 10-30 seconds after the delay first happened, they'll all complete rapidly in succession. The same thing happens with grinding.

This also happens with getting in and out of cockpits. I'll press "F" and nothing will happen, no sound effect even. The other player can see that I got into the cockpit, but for me, I'm still floating outside. 10-30 seconds later, on my game, I'll go into the cockpit and I'll hear the sound effect. Same for cryo tubes, and similar for getting health from the medbay.

It definitely seems like something isn't syncing properly with my client. The other player has none of these problems. He has 70-100 ping, I have 70-150 ping. Both of our client computers are plenty powerful. The other player doesn't have these problems, so I don't think it's a problem with the server hardware. With shift-F11 I can see that sim speed (both local and DS) are at 1.0 or 1.02 nearly all the time. They do drop very occasionally, but it doesn't seem to be linked to these sync delays. Render CPU and GPU hover between 90-100%, but I'm always close to 120 FPS. Thread CPU load is usually around 125%. All the server threads show below 30%, with the server thread one usually much lower

Final note: I do have experimental enabled, and some mods and scripts installed. However, this was happening previously (still on 1.187) with very minimal scripts, and very minimal (skybox only) mods.

I'm happy to supply whatever files are helpful, or try various things. This is very easy for me to reproduce. It basically happens constantly.