Hm, your file processed fine here. So, at your screenshot, I do see the \" tags. That is probably the issue... No idea why they end up there, but I'll have to edit my script to allow this "type" as well...
I've just added some "real-time" checks. Good idea!
I got the error message about thumbnail and license only when the file (pretty big) was uploaded.
That is because the license and thumbnail are reset when there is a problem. The file is not uploaded btw, unless everything is error-free.
The license checkbox setting is now saved after submitting, but I cannot save the file (due to security risks), so you'll have to reselect the files each time. However, with the "live" checks, this should occur less often.