PsychoPy becomes unresponsive in FullScreenMode

Hey there,
I’m using PsychoPy3 on OS Win10.
I was building my experiment basic structure with the Builder, continuing now in the Coder.
My experiment runs on two monitors, which display similar stimuli. I am encountering a problem when setting the windows fullscr to True.

SCREEN_SIZE = (1680,1050)
win0 = visual.Window(SCREEN_SIZE, screen=0, fullscr=True)
win1 = visual.Window(SCREEN_SIZE, screen=1, fullscr=True)

When its set to False, the experiment runs perfectly fine. When it’s set to True, the experiment will freeze right in the beginning, the program displays a grey screen on win0 and flashes a screen to win1, which then disappears again, so that the experiment doesn’t start at all. At this stage I can’t exit the experiment at all anymore, having to force sign off the computer by Ctrl + alt + del. I haven’t encountered this problem, when setting only one monitor up.

It’s probably a very easy fix, but I don’t get it at this point.
Thanks in advance!
Jana