Shotcut cashes: Linux Mint - non-admin-user

Shotcut-Version 20.07.11 on Linux Mint 20 Ulyana base: Ubuntu 20.04

When I use ShotCut as non-admin-user, the app starts well and I can load Videos into the app (drag-and-drop)
When I pull the video into the timeline the app crashes.

ALL this activities I can do as admin-user without any problems - the app works fine. I tried to change some rights to the restricted user but had no luck.
Is there any idea about the cause of the problem ??

I am using the flatpak-version of Shotcut 20.07.11 on Linux Mint 20 Ulyana which is also offered by the built-in software manager of Linux Mint.
It works all fine here, also as an non-admin-user.