We’re running into the same issue mentioned in Screen shrinks to the top left of the screen Windows Player. When the display turns off (or changes input) when the display reconnects, Xibo player has shrunk to the corner of the display.
It looks like a fix to the player was committed, but we’re running the 1.8.8 player and still seeing the problem. I can also confirm that the registry fixes mentioned in the above don’t work anymore either.
Any help I can provide troubleshooting this, by all means let me know.