We have a 3300 8.0 UR4 with 2 ASU 16 port devices attached. We've had various fax machines and speaker phones on these ASUs for 3 years and have never heard of a problem. Recently people have been getting communication errors and sometimes faxes get cut off on 3 different fax machines on 2 different ASUs. I've tried different fax machines and I've tried different ports and it made no difference. Fax machines with POTS lines haven't had any trouble so I swapped a POTS line with an ASU line to see if the trouble would follow. To my surprise the trouble had cleared when the lines were swapped, but started in again when they were put back to the original position. Unfortunately leaving them swapped isn't an option. When ASU line was in a Brother fax machine it was having issues, when plugged into a large Sharp printer/copier with a fax board installed it worked fine. Two of the fax machines having troubles and the POTS line fax machine are approximately 400' (rough guess) from the ASUs. The other fax having trouble on an ASU line is only about 50' away from the ASU.
It seems odd that both ASUs would start having issues at the same time. I have also tried resetting both units and took steps to eliminate RF. Nothing had really changed in any of the enironments before the trouble started. Also, nobody has reported issues using the speakerphones in conference rooms which are attached to the ASUs.
Has anyone ever heard of fax machines having troubles with ASUs and if so, are some machines more susceptible than others?

Swoby