Experiment is not shown in Full-Screen

Hey there,

my Experiment is starting in full-screen for maybe half a second, then snaps back to the windowed mode. I tried adapting the screen size:

WIN_WIDTH = 1024
WIN_HEIGHT = 768
POP_TEXTURE_SIZE = (200, 155)
BALL_TEXTURE_SIZE = (596, 720)
INITIAL_BALL_SIZE = (
int(BALL_TEXTURE_SIZE[0] * 0.2), int(BALL_TEXTURE_SIZE[1] * 0.2))

win = visual.Window(
size=(WIN_WIDTH, WIN_HEIGHT),
units=‘pixels’,
color=‘Black’,
fullscr=True

and I also configurated the monitor properties (ticked the ‘full screen window’ box, adapted the size accordingly).
It’s the same in piloting and run mode. I also tired deleting the specifications in the code, having the same results.
I’m using v2024.1.4 under Windows 11, but tried other Psychopy versions as well with the same result.

I’m quite new to PsychoPy, any help is appreciated!
Thanks!