RE: Error 500: Internal Server Error - when submitting
Today was the first time I tried and its my first add on submission.
Before when I tried to submit details, like the support url - I didnt use "enter" key and the UI kept going (red bar on top gone through) and "circle" spinning, without finishing correctly (not going green).
I then rechecked the button to save this details, and the field got flagged okay.
And before the error the first time appeared, I set the category for the add on, which I missed in first place.
So, my best guess would be, something got broken on the UI/background of the submission page having a hick up...
After I canceled the initial process and redone everything, it was fine. I didn't make any changes to the data or inputs itself on that submission.