Do you remember what you typed into the description box? (more importantly how you typed it? when you placed new lines, how you removed them?)
This kind of exception should be reproducible, however even though trying for 10 minutes I couldn't get it to crash.
// Edit // Nvm, just got it to crash by spamming the keyboard, now I just have to find out what I spammed.
I had quite the long description when it crashed. I believe it was 5 lines long, and it was 7 lines when I collapsed lines 2, 3, and 4 into line 2. (All of the lines exceeded the box, and had to use the arrow keys to view all of it.)
This, by the way, is after a failed upload of the same Replay, when it displayed the "Description is too long" error when it finished. I tried again after trimming some text from several lines (removing redundant/not needed words), and that was when it crashed.
After I cleared my client's list of uploaded Replays , the Replay uploaded fine (this time, I used a much shorter description with only 3 lines).
(All of the info above I'm recalling in retrospect, may not be 100% accurate.)
Could you add the character limit for descriptions to the documentation? Would be appreciated <3