Thanks Maijestro for the video and explanations.
Okay, the video is fine now; it all depends on how the YouTube video was encoded.
But I still have a problem: the audio cuts out at a certain point.
I've tried different versions of YT.rexx, but it doesn't change anything.
I've changed my screen resolution, disabled everything in WBStartup and in user-startup, and tried with different videos, but the audio cuts out again.
Here are the videos I tested with.
https://www.youtube.com/watch?v=PgC-rNaBh7Y&pp=0gcJCT8LAYcqIYzvhttps://www.youtube.com/watch?v=wN7QX_pwoIwhttps://www.youtube.com/watch?v=tnboohDM3ughttps://www.youtube.com/watch?v=bzZjG9B9_Ug&pp=ygUHY2Fubm9ucw%3D%3DI'm stumped, I don't know what's causing this?