Module of Practice Exams keeps crashing and I cannot open the current version

I am working on a module of practice tests with a series of test banks. My file is very slow to save and has several times locked up and I cannot reopen that current version. I get a message that says "The project "Storyline" is locked by another process". Moving forward I will change the version each time I save. I am saving after each operation (ex: formatting slides in a scene). This seemed to start this week so I reverted back to the April 11th version. This has cost me a considerable amount of time and I am getting very frustrated.