Mouse-look stalls on a ~5.37 s cycle; keyboard and menu cursor smooth (9950X3D, RTX 5080)

GAME / SYSTEM

Game version: Latest available on the Steam

OS: Windows 11 26H2(26300.9457)

CPU: AMD Ryzen 9 9950X3D (AMD Chipset Software 8.08.12.551 installed)

GPU: NVIDIA GeForce RTX 5080 16 GB, driver 617.42(Latest, Game Ready)

RAM: 62 GB

Motherboard: ASRock X870E Nova WiFi

Mouse: Razer DeathAdder V3 (800 DPI, 1000 Hz)

Display: 2560x1440, fullscreen, game adapter = RTX 5080 (an AMD iGPU is also present)

PROBLEM

During gameplay, mouse-look periodically stops working. The camera stops turning for a short moment while I keep moving the mouse, the character keeps running, and then the camera catches up. I have been seeing this for months. It happens in a newly created world too (Colonization scenario).

- Only in-game mouse-look is affected

- Keyboard movement (WASD) is smooth

- The mouse cursor in the game menus is smooth

- Desktop, CS and all my other games are smooth

MEASUREMENTS (from the attached video: https://youtu.be/hI7CfPpqajk )

A frame-by-frame analysis of the 60 fps recording (done with a script, using the horizontal shift of the background between frames as a proxy for camera rotation) shows that the stalls follow an almost periodic cycle of about 5.37 s: 10 events at about 18.8, 24.2, 29.6, 34.9, 40.3, 61.8, 67.2, 72.5, 77.9 and 83.3 s, each within 0.02 s of a 5.37 s grid. Between about 43 and 59 s the camera is not being rotated (the character runs straight), and the cycle stays in phase across that gap, so it looks like a free-running timer in the game or system rather than something driven by mouse events. Each stall lasts about 0.15-0.2 s. During the stalls the image keeps updating at close to 60 distinct frames per second in the recording; only the camera rotation stops. The in-game FPS is about 120-145.

The recording was made with NVIDIA recording and its on-screen statistics (visible on the right). The first ~2 s and the last ~1.5 s of the video contain unrelated frame hitches, probably from starting and stopping the recording. The freezes also happen with the NVIDIA and Steam overlays turned off.

WHAT I HAVE TRIED (no change in any case)

Hardware / USB:

- A second, different (office) mouse: same freezes

- Different USB ports: same freezes

- Disconnected the extra mouse and keyboard that were also connected: same freezes

- Mouse polling rate 125 Hz (default 1000 Hz): same freezes

- Full PC reboot: same freezes

- Re-plugging the mouse or any other USB device only delays the next freeze (about 10 s instead of 5-7 s), then it comes back

Software / system:

- Steam overlay and NVIDIA overlay turned off: same

- Steam Input turned off for the game: same

- Network completely disconnected: same

- Razer Synapse does not start with Windows

- Installed the AMD chipset drivers including the 3D V-Cache Performance Optimizer and enabled Xbox Game Bar "Remember this as a game" for Space Engineers 2. The game now runs on the V-Cache CCD (logical processors 0-15 in Task Manager). The same freezes happened before, when it ran on the other CCD.

In-game settings:

- Graphics preset Low (all graphics options at the lowest value)

- Windowed mode and VSync: same

- Autosave off, data/contact sharing off: same

RESOURCE USAGE (Task Manager while playing)

CPU about 6-8% total, RAM about 17 GB of 62 GB, disks near 0%, GPU utilization about 98-100% at an uncapped ~120-145 FPS even on the Low preset.

EXPECTED

Smooth camera rotation, like in the menu and in other games.

Please tell me if you need logs or any specific tests.