Reverts to Windowed mode?

[Sailboat]

I have the graphics "screen/UI resolution" set to 1920x1080 (desktop).

 

Periodically, it reverts to "windowed" mode, and then always displays the Windows 10 taskbar at the bottom of the screen while in-game.  I cannot select UI elements down there, I get taskbar stuff.

 

Fix is easy -- reset to 1920x1080 (desktop).  But why does it revert from that setting to Windowed, and how can I prevent that behavior?

[WanderingAries]

Sorry to hijack, but it's the same thing.

 

I've not played much this summer, but I have been making alts and such this week. What I've found are two things:

 

1) My first launch of the game from a cold boot results in the GFX defaulting to Windowed Mode;

2) If I click to launch either too quickly or to intentionally launch a 2nd instance (two accounts) too quickly, then the second instance triggers a warning (didn't open correctly or the like) and puts That instance in safe mode;

 

The "fix" for both is to wait more than 2-3 seconds between clicks with every instance afterwards opening in my normal 1080p Desktop Mode. I hope that narrows it down, but it's a new annoyance, now that I can see what I've been reading about this past month.

[Sailboat]

Update:  still getting this regularly.  However, it seems to be associated with tabbing out to the desktop.  If I tab out a lot, like to consult Mids, it goes into Windowed mode until I reset it manually.