I am using the version 22H2 (build 22621.2715) of Windows 11 Home on my 4½-year-old laptop. I still use the Shotcut version 23.11.29S. Sometimes, the time line uses a wrong time format, as you can see here. This is a low-priority bug that is perhaps deep in the “kernel” of the program.
Oh, 60 minutes instead of rolling over to another hour. This might depend on the project frame rate. Can you tell us what it us?
I’ve tried many things. But I am not able to reproduce this. Can you give us any more clues to reproduce it? Maybe you could make a project using a color clip that shows the problem that you could share with us.