The symptom is when you go to other app and come back to Photoshop, the canvas becomes blank gray. I have to move some objects or hide/unhide some layers for the screen to come back again. See the attached you to see what it's like.
This is so annoying because we have to use back and forth between apps.
I've tried changed GPU preference (Basic/Advanced and even NO GPU) and re-started photoshop but it didn't solve at all. So I think it's not about the GPU setting.
Finally, I find a solution but it's not actually practical but it worked. I noticed that it happened to some artworks that has Artboards so i tried to clear all artboards inside that artwork. The symptom is gone (not entirely but it happens less)
To Adobe, please fix ASAP. We need to use Artboards.
To fellow users, if you have better solutions, please share.
Now I've downgraded to 21.12 because I cannot stand this bug. (21.13 has the issue of freezing when usine Brightness & Contrast with Ruler enabled).