It's probably due to me rebooting to load new code, I will have a way to send a signal to the frontend to inform them but not implemented atm
edit: don't know if you'll see this any time soon, but I've had it fail/hang again. You might want to take a hash of uploads, so if the lost connections still end up getting transcribed, if they're reuploaded they won't get transcribed again.
Also I haven't had success in Firefox, only Chromium.