This might have always been the case, rustynails. I just noticed it when working on the server yesterday.

Right now the fax ports are connected through our Shoretel PBX and out a dedicated PRI for faxing. However, I only moved the lines yesterday afternoon to route through our phone switch. That was done to work around a separate issue, which is now fixed. I haven't moved them back yet, but in either case the logs show the issue had been happening even when all ports were connected to POTS lines.

All of the stand-alone fax machines that I currently have are connected through our PBX. What I could do, however, is connect a fax to one of the POTS lines that I was using for the fax server and test that way.

Understanding that fax communications are never going to be perfect, this may be a non-starter. It just seems a bit too many of these errors for my liking. Plus, I'd really just like to know what might cause a "late disconnect" to occur.

Sometimes you carpe diem, sometimes your diem gets carped.