This is a new bug as of version 21.05.01 unrelated to GoPro. The recommended stable version on the download page is 21.03.21. I just fixed this for the 21.06 release, but it is not in the release candidate.
with issues (Jobs screenshot).
This is a minor issue with the way ffmpeg reports its progress with videos like GoPro that embed timecode. I have not found a way to fix it.
cause Shotcut to freezes when added to the timeline
I think you are experiencing problems in version 21.05 that were addressed in the new 21.06 release candidate. It helps to know how you are adding to the timeline since there are many ways.