I have encountered this as well. Often when I switch from another workspace back to the game, I can't turn to the right, it's like moving the mouse to the right hits a wall. Goes away when I again switch to another workspace and back. (I have my workspaces bound to numpad keys, so switching back and forth takes less than a second and requires no significant effort, but it's annoying nevertheless.)
I get this in all 3rd-person shooters I've tried.
I just tested a game where while playing it happened but fixed itself too during control change events (eg scenes that take away control then give it back).
So looks like alt+tab, etc may not be required to fix it, though playing until it fixes itself, may generally be a bit too much.
Quick update: it also occurred in Prey (480490), in the intro after you leave the helicopter. However, this time the angle was more like 45-70 degrees instead of 90.
It happens when the focus gets lost (with Steam overlay/window switching) in Unreal Engine 3/4 games. There you need to right/left click. In HITMAN 2 (https://github.com/ValveSoftware/Proton/issues/2121#issuecomment-503254964), you need to change the display setting to any other you want (fullscreen/exclusive/windowed). Otherwise you'd get locked inside a ~60° (default FoV) angle cone mouse rotation.
I have had this occur in Witcher 3.
Side note: I have two screens, a main one and one to the right. As the movement in game stopped, the mouse would fly out on the right screen if I recall correctly. I've only had this occur when moving my mouse "too far" to the right.
Quick update: it also occurred in Prey (480490), in the intro after you leave the helicopter. However, this time the angle was more like 45-70 degrees instead of 90.
I can confirm. To reproduce this in Prey do not open menu and inventory for a 20-30 minutes.
Also occasionally happens in Battlefield Bad Company 2
When using a tiling wm, the issue is worsened, as it is sometimes impossible to fix without restarting the game. And, to clarify, it's not that the camera is locked to a specific sector of rotation, it's limited to the bounds of the screen. The difference in areas is likely due to a difference in mouse sensitivities. I've found through personal testing that the issue is display server agnostic (e.g. it occurs in X and Wayland).
This particular bug occurred for me while trying to play the landfall archives, but I have encountered a worse bug (potentially unrelated) where the game does not receive mouse movement info whatsoever (happened to me trying to play ultrakill a few months back, never resolved).
I think I may have found a workaround. Try enabling only the screen where you are playing the game, and disable all others when gaming. This seems to have fixed it for me.
When I have both displays on, sometimes it works fine, other times a similar issue happens when I play the Finals. On the other hand, the workaround didn't reproduce the issue again.
System Information
I confirm:
Symptoms
I've encountered a bug in certain 1st/3rd person games where instead of being able to rotate around 360 degrees and beyond like normal, the camera gets locked to a 90-degree area and I'm unable to rotate the camera beyond that area. Fortunately, it can be fixed by alt-tabbing or pressing the super key, but I shouldn't have to do that.
Out of all the games I've tested [Oblivion (22330), Empyrion (383120), Subnautica (264710) (experimental branch), Fable Anniversary (288470), DOOM (379720) and Warframe (230410)], it has occurred in Empyrion, Subnautica and Warframe, although I am still in the process of testing Oblivion and Fable Anniversary. I obviously believe this to be a Proton problem since it isn't unique to one game.
Reproduction
Unknown. It happens at random; there's no one scene in any of these games where it only appears.