What is your operating system? Ubuntu Linux
What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit? 21.01.29 / 64b
Can you repeat the problem? If so, what are the steps?
Entirely repeatable ad nauseam until I figured out a work-around.
I have a project called “m2” (so the project file is m2/m2.mlt) and this includes a source file called “m2-reversed.mp4”.
Now whenever I save the project, quit shotcut and start it again to do more editing, I would get the missing file popup, where it complains it can’t find the file /path/to/m2/-reversed.mp4. Needless to say I hadn’t moved the file, it’s just shotcut looking for the wrong file name.
So I double-click, select the correct file, everything works fine, until I finish editing and the next time I start shotcut, it I get the same popup again. The simple solution was to rename the file to “reversed.mp4” and now the problem has gone away.
It does suggest though that shotcut has a problem when saving the project file with source file names that start with the same characters as the project name (i.e. it tuned “m2-reversed” into “m2/-reversed” because the project name is “m2”).