Steps to replicate the issue (include links if applicable):

• Go to https://commons.wikimedia.org/wiki/Special:MediaSearch?search=Birds
• Click on an image to load details panel

What happens?:

• The image part of details pane throbs forever
• dev console shows things like: GET https://upload.wikimedia.org/wikipedia/commons/thumb/9/93/The_Asian_Paradise_Flycatcher.jpg/640px-The_Asian_Paradise_Flycatcher.jpg [HTTP/2 400 Bad Request 58ms]

What should have happened instead?:

• Special:MediaSearch should have requested the correct thumbnail size for compliance with T414805