Does it happen only to that one project or shotcut in general?
If in general, then clean up the settings. Rename this directory and this file
(see https://shotcut.org/FAQ/#where-are-the-log-presets-database-and-settings-stored )
If you need some clearer guidance, here’s a video:
If that doesn’t help a screenshot would be nice
If it’s specific to your project, you could try sharing the .mlt file with us. Check the file (it’s a text/xml file) for any words (username, filenames) that you want to keep private first. If you replace the words carefully, we should still be able to try out the project.
You can use https://gist.github.com/ for example to host your file and I think this forum has an upload feature too.
PS: What’s your screen resolution? (just in case you’re using a super small resolution and that somehow screws up shotcut’s UI)