I'm checking out a few pages at random and I'm not able to replicate the issue you guys are having. It might be a result of the thumbnail reconfiguration I recently did. We had a problem where viewing pages on certain devices regenerates all of the thumbnails and our disk space was very quickly filling up. I fixed that problem, but it seems to have created a new one.
Getting thumbnails to work on MediaWiki is rough. Every solution either A) slows down pages to a crawl B) uses up lots of disk space or C) breaks thumbnails on certain devices. I'm heavily considering moving the site to a new host so none of these are a problem anymore. Until then, I'll look into this issue and try to find a universal fix.