I've seen a few alerts for the phabricator phd process. It always recovers immediately but there might be something going on with the queue processing. I'll look into it.

Unfortunately I didn't find any useful clues in the logs.

Same thing happened with 1,2 MB files, I think the problem is with thumbnails of files of certain size and up

https://phabricator.wikimedia.org/T280497#7358938

Hmm, perhaps it's hitting a memory limit or something? The limit shouldn't be a problem with such a small file though (unless it's doing something incredibly inefficient.)