Uploading anything breaks firefox somehow?

Info:     Description of setup Firefox 62.0 (64-bit) Addons and extensions are disabled Windows 10 JS seems to be enabled because everything else works except uploading Current Antivirus is Avast however it too was disabled for some testing. Web console shows no action while this happens so no logs of the event exist. Issue: I can't upload anything to roll20 from firefox. Chrome does work so this is a mild inconvenience because I'm not a chrome fan. After 3 hours of testing I can tell you that when trying to upload anything from firefox the entire browser stops sending or receiving data. Input works but I can't go anywhere nor refresh pages. It doesn't freeze. Task manager shows it working on ?something? as it's not at idle. From here I can either close firefox and reopen it or close the upload popup and wait 5-10 mins for it to finish whatever it's doing. Aside from uploading images everything else works. I have no idea how recent this image is because I havn't uploaded anything for over 2 months across multiple games. Please help: This is really annoying . I have a game in 10 hours and still need sleep.

I want to mention I've tried files of all 3 types and many sizes under the 5MB limit.

Hang on M_Leon246. I'll ping a dev.

So I just tried it again in my game today and it was still happening. (to make sure it wasn't just some random issue.) Then I tried it in a test game my group shares for macros. I'm GM there too so it would seem to have the same settings. It work in that test game... Ok sure. So It's my game. I go back to my game and start the upload to get a screenshot of console not moving because it doesn't do anything when whatever this is happens. Upload works now. In my game. A few clarifications: It's not that firefox stops responding. I can open/close tabs or do any number of things. It's just that anything that would require internet didn't work (the red connection error block would popup in roll20 if I left it going long enough) and that console log wouldn't move anymore. CL acted like firefox was idle. I had task manager up for some of the testing when it was happening. Firefox was using 21% Cpu and an additional ~100MB ram 0%disk and 0%network during attempted upload. I'm on a i5-8600k for reference. Firefox idles at less than 1% without me touching it. I used the CPU spike to time how long this would take to resolve itself. That is where the 5-10 mins come from. Over 3 hours of playing with it I can say that the time seems random between that interval regardless of upload size or type. So it works now.  Edge case? Hate to drag you guys away for something like this. I really thought it was some major issue. Thanks though... I hadn't thought to try another game so in a way you did fix it. Addendum: For whatever reason there isn't any pulsing upload bar anymore. Just a blank section where some kind of % bar should be. Unrelated but it makes me think upload isn't working even when it is.