I get this glitch occasionally.
I'm not sure why it happens, but it seems to be that after you spend a long enough time on the submission page, something times out and it won't submit.
I used to think it was just my login timing out, which happens occasionally (obviously as a security measure), but I've had this happen to me a few times and I would still be logged in... it would simply take me back to the homepage, and my entry would not be shown under "Recent additions"
Luckilly, I'm able to hit the back button and all of the forms are still filled out, where I can simply just hit submit and it'll normally go through the second time (In fact, for me, personally, it has always went through the second time).
Perhaps this just has to do with connection speed/ reliability?
My connection isn't the most reliable, so maybe if it cuts out for a second or two, it won't send the proper code from the submit button, and therefore won't add the submission?
To be honest, I don't actually know much about programming, just most of the concepts of how it works, and barely any of the syntax.
Anyway, not a huge deal since it's so easily fixable, but this has been my own experience with it.
If it helps with debugging, I'm using Google Chrome (v26.0.1410.64 m)