I find this sometimes, when I’ve posted a lot of stuff on there, but it has always been temporary.
Yes, when I was editing and uploading dozens of lectures in a short period of time I got rate limited. If I recall correctly, the messages said I needed to wait 24 hours to regain upload access, but I could upload again after several hours.
Researching it at the time, so I could appropriately pace my uploads, I found the limit is based on some secret and changing algorithm, and there isn’t any simple rule anyone has figured out.