Doesn't seem to be size related, as a 50MB file will upload first try, while a 5MB one fails 10 times.

Other files won't upload after 10 tries. This is really confusing. If this was a file transfer issue, I would expect a very different message.

Alright, after trying to upload the same file the third time, it completely succesfully.

Well this is curious. Just now I managed to upload the File I linked in the original Post.

The next 3 files still had the same error.

Alright, the 100% issue seems to be resolved. Now the videos that were stuck at 100% can upload completely. But the videos that got the "File type not allowed" Message still won't.

I'm noticing that the videos that do upload were rendered from Vegas and the ones that don't rendered from MeGUI using the x264 codec.