I've seen this recently and here's what steps I had taken which caused it, may provide you an answer. We've recently built out a few RF boxes and I was performing testing on the channels and of the DIDs, I had the server (not in production) try to process 20 faxes at a single time (between 2 servers each with 30 channels) and RF Util would show scheduled to be sent (way back). I suppose it's due to the work load on the server (in terms of how many faxes need to be sent and the number of pages). As for the transmission error, I'm not sure if it's related as the faxes were sent successfully.