While I'm in a Steam game, any time I open up any kind of UI menu and then exit the menu, the camera (character's rotation) will snap to the movements I made in the UI as soon as I touch the mouse again. It's almost like mouse look is not disabled when the UI is open. Has anyone else had this same issue?

I've encountered this in many different games. To name a few: FortressCraft Evolved, 7 Days to Die, Stranded Deep. There are others, but I can't remember them off-hand..

In most cases, I've found that if I bring the mouse cursor back to the crosshair position (or center of screen) prior to exiting a menu, the player rotation won't snap elsewhere. But it's so irritating to have to do this allllllll the time.

I'm running OSX Sierra (10.12.6) on a MacBook Pro Late 2013. My steam client application is always up-to-date (afaik). Built on 3/26/2018 at 14:30:04. Steam API v018. Steam package versions: 1522101301. All my games are also up-to-date. Also, the Steam overlay is disabled.

I have no idea if this is a Steam issue, or just a Mac OSX issue. But that said, I've never encountered this on any non-Steam games I've played on this same laptop.