I just uploaded some pictures, and most thumbnails have horizontal black lines. Original size is not affected.
Concrete exemples (includes one of mine) already reported here: https://commons.wikimedia.org/wiki/Commons:Upload_help#Thumbs_have_horizontal_lines
Many of the new files seem to be affected as well: https://commons.wikimedia.org/wiki/Special:NewFiles (interestingly, we don't see any horizontal line in most of these thumbnails, but if you choose randomly a picture, the bigger thumbnail depicted in the file's page will likely have these horizontal lines).
A few hours ago, I uploaded a picture without any problem.