Grease Pencil issue when updating Blender to new version

Hi everyone!
I’m working on a small 2d project with grease pencil. I started it with Blender 2.82 and since then every time I tried to update Blender, the new version completely breaks the scenes I’ve already made. I tried with blender 2.83, 2.9 and now 2.91.

Here you can see what I’m talking about:

These black lines are everywhere and they show up in the rendered animation too.
I tried to search on the internet but found nothing. Does anyone know why this happens?