It is strange that Shotcut works very well for most people but a few people have trouble with it. We can’t always dig into the problem because it is specific to the user environment.
The two most common problems for people are:
- Incompatible GPU/Display environment
- Something unique/uncommon about the media files being used
To see if either of those relate to your situation, you can try:
- Use Shotcut on a different computer and see if the problem persists
- Use media files from a different source (different brand camera, etc) and see if the problem persists.