Had the same problem. Created a gallery with 200+ images but Bootstrap Studio crashed everytime I saved my project. I resolved it by reducing the size/quality of the images.
I also contacted the developers to let them know about the issue.
@Martin responded:
In general storing large galleries in Bootstrap Studio can slow down
the app. We will work on this in the next releases. A not-so-difficult
workaround is to keep large images outside the app, and only reference
them by URL.