I've was visiting family in Florida in Jan & Feb. They have an old-fashioned AT&T POTS line and two different AIO printer/faxes, While I was there I ran some tests, and 4 of my 6 test calls to my inbound fax number failed. Since returning home, they've tried to send me another 6 fax calls, 4 of those failed. That's a 66% fail rate. I alternated the two different AIO's on the line, but that made no difference. However, while down there I also sent some large (30-to-40 page) faxes to other fax servers using that same POTS line and those same AIO's, and those calls went through and stayed solid to completion.
Also, last Friday, I requested an insurance company to fax me a couple of forms. One of their fax came in fine, the other died from a communications error. I requested a retransmit Monday, and that came through fine.
I described the problem to Eddie in Tier 1 support today, and he suggested posting here to see if other users are having similar issues, and to put the problem on "Labs's" radar. So here it is. Get in touch if you need more details.