Steps:

1. Export a snapshot of the project
   
2. Once you export a snapshot you can close your project and open a new one. (Don't worry it is saved)
3. In your new project import your snapshot and then try to save.

It should work as intended as the import should fix the timing issues that the project has.

The issue is that the user may have imported or made a line with a timing issue, this can happen if you edit a line and maybe not pay attention to the start and end times are shown in the timeline view.