Frames erased but not gone (Mac)

@BrooklynTheGreat I also found this which was uploaded 1 week ago so it should be relevant:

i must have a different version than that, because mine is all black with white print, and it wont let me upload anything from my actual files. it has its own little file system that doesnt help anything, and theres not way to get my animation in unless i copied the file and pasted it onto the file system there. i did it, and “my clip is invalid, it will be removed from my timeline”.