This file is not displaying properly at mediawikiwiki, but it looks fine on Commons.
I've tried purging the file page at Commons and Mediawikiwiki, and purging a page it is used on. That didn't help.
The only clue is the "0 x 0 pixels" metadata. Possibly that means it is related to T192866 ?
https://www.mediawiki.org/wiki/File:Mobile_Page_Issues_Research.pdf (0 × 0 pixels, file size: 1.32 MB)
https://commons.wikimedia.org/wiki/File:Mobile_Page_Issues_Research.pdf (1,500 × 843 pixels, file size: 1.32 MB)
Missing thumbnail generation can be seen at https://www.mediawiki.org/w/index.php?title=User:CKoerner_(WMF)/sandbox&oldid=2765329 where the link on the right should actually be a normal thumbnail.