Something's wrong with the diff display:

It's possible that this is a test-only issue, but superficially it seems to be an edge case that might be reachable from production. The bottom pane should be a preview of the latest revision, but instead it seems to be a diff between older revisions, probably related to a special order of clicking around the interface.

The gray "loading"-state diff breaks several tests which are waiting for the loading style to go away.