Solved: I took another look at the Permissions page in Studio. That's when I had a breakthrough thought. @Alex T⚜️ mentioned the membership limit. My Admin account has no file limitations. I had set strict quotas on storage and max file size for Unauthenticated and Unconfirmed. Since the original Admin account does not go through the same on-boarding process as all the other accounts, I tried removing the limitations on those two types. As soon as I did, I was able to upload any video I want! I can now upload videos longer than 3 minutes and 30 seconds. Since the original Admin account does not go through the manual email verification process, I believe the file limitations I had set in place were affecting my own account. I still have the problem of the CPU peaking at around 95% during conversion, but it slows down once it is done. But that was all it took to get all video uploads working.