i had a similar issue with my previous monitor and a few games. for some reason the resolution and/or window settings would be altered for some games.
at certain settings some games would either be auto-minimized or would even show a black screen until i alt-tab or alt-f4.
some times i could alt-tab back to a windowed game and manually reset the resolution and fullscreen settings. other times i had to locate the game's .ini file and manually enter the correct data. usually the settings would stick after re-entering them and the games would function fine.
maybe give that a try.
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