Hey Mathilde,
when I realized that it was only one specific file that was affected and not a general problem, I decided to rebuild it in a fresh new file. That seems to work now.
It was not so easy to share the file or do a screen recording as it is a file I don't want to show in public.
Anyway: If your are still interested in the issue let me know cause I appreciate CryptPad and If I can help...