I just switched api providers working on sorting that out. I think it's mostly when the api won't process it for safety reasons. With the new provider the room is getting stuck occasionally when the content gets a lil risqué.

Im str8 pushing to prod so we will see if it gets better or worse

It's an HTTP 422 code. Some web frameworks use for validation errors, like fields containing prohibited values.

Depending on the application, the incorrect content type on a file would be considered a validation error, instead of a bad upload.

Fun bit of trivia: 422 was originally a WebDAV code, but frameworks like Ruby on Rails started using it for validation errors in forms.