https://commons.wikimedia.beta.wmflabs.org/wiki/File:Crystal-NEW.stl
This file, uploaded since thumbnails for other files was fixed (see other files around it at https://commons.wikimedia.beta.wmflabs.org/wiki/Special:NewFiles), does not thumbnail correctly. I tried to debug, but apparently my logstash-fu is insufficient to glean anything useful.
As far as I can tell, thumbnailing is working locally, so it's probably another beta configuration issue that we missed.