Hello Cambray,
Sorry to hear that you ran into this issue.
Can I ask if you are working locally when making changes and saving your project file? Working on a network drive can sometimes cause issues with saving, issues brought about by the introduction of latency.
If you're already working locally, I'd like to see if I will be able to save your project file using the latest version of Storyline 360. Would you be willing to share a copy of your project file here or in private by opening a support case so we can take a look? We'll delete it when we're done testing!