Hey JBroderick,
Firstly, make a copy of the Project you are having issues with so you have a backup. Next, go into your copied Projects folder directory and located the ‘Saved’ folder. There will be a folder created if you have any Matinee recordings saved into another folder labeled ‘Video Captures.’ Open this folder and delete any saved video files within, and then attempt to open the project.
Let me know if this resolved your issue or if you need further help.
Regards,