Get 404, page not found error when posting

I've had a few times where after hitting "submit" i get directed to a 404 error page and, naturally, lose everything I've written. This is, of course, frustrating even if I'm wary enough to back the stuff up on my clipboard.

Still trying to reliably replicate it, but I believe you can if you let the submission page sit for too long, i.e. 10+ minutes.