NNBR1

Literally any picture link, with :large, or with :orig. I disabled all my addons, and the problem persists. The URL structure is https://pbs.twimg.com/media/[filename].jpg:orig. Any URL using this will fail consistently....

I am using 2.5.6 with default settings (delete/reinstall addon). Immediately, I get a "Failed downloads: 1". I was using this random picture as a test, refreshing all tabs inbetween attempts....

Weeeeell. At least the culprit has been found, and if it's up to Firefox to (not) solve, then I guess case closed. In case someone else finds this error, maybe...