Creeping reprojection in VR

Hey Unity team,

We have a really unusual issue where if our game window is not the top window in the windows hierarchy, it will slowly start to accumulate lag and reprojection, visible in the SteamVR reprojection window.

Clicking the minimize and restore button clears this out and returns us to full FPS.

Does anyone have an idea what might be causing this? We have video evidence for a more detailed investigation, but are a bit stumped at this point.

Any new information would be greatly appreciated!

 

As dodgy as this is, we wrote a method that forces the Unity window to minimize and restore every couple of minutes which keeps the game running smoothly throughout the experience. It's a total brute force solution, but with no insight into the cause there wasn't much else we could do.

Would love some insight here!