was about to say, Oop, op fixed it somehow. bug reports always ask for reproduceable steps. if you know maybe they'd be interested enough to prevent in the future. I think anyone can submit an issue. for sure with a GitHub account.
https://github.com/LemmyNet/lemmy-ui/issues
seems like i dealt with this years ago when doing some wordpress forms. uploaded file gets dropped after thumbnail processing. coding error. like the post was incomplete like you mentioned