A strangely similar problem. Turns out they were not hitting the Windows key but had installed the Mouse Driver and App that came with the mouse. Fix? We removed the mouse driver and app that came with the mice to force use of the Windows native drivers. It stopped tabbing out to the desktop.
Hope this helps.
Why do some games i own not all tab me out after a few to many click (its not my mouse i have tryed 5 different mice) and some take along time to let me back in as in i click them 100 times before it starts to get me back into the tab. Also some don't tab me out just make it windowed like minecraft i just have had this extremely erritating problem for along time and would very much like a solution.

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