I crash EVERY time I OPEN a project that was started in a previous version. The only way I can proceed is to create a NEW project in 15.1, the IMPORT the sequence from the old project. Then I can work on it, but if I save it and close it and quit PP, it WILL CRASHH AGAIN IF I OPEN THAT SAME PROJECT, so I have to do it again. I have to make a NEW PROJECT EVERY TIME, and import the old one. SHEESH! This is terrible.
Sounds like your project might be corrupt. Sorry about that. Do you have any backups of the project you can work from? Any way you can return to 14.9 to complete this project? As you may know, it is not always a good idea to update a project across a major update.
If you can generate a crash report, upload it and let me know. I can ask for help to see if there is anything obvious preventing your project from behaving normally.