Ace, sorry I did not get back to you on the previous thread.
I did talk to Martin about DDEC II issues. He said that he was aware of the early DDEC II issues where the ECM does not display miles. That is where the prom replacement might help: http://www.busconversions.com/bbs/index.php?topic=15734.0.
However, you have an '92 and that should not be an issue. Also, I think you said that you could see the data on your Pro-Link.
I have been working with a customer who has a '93 and VMSpc. He was not getting mileage numbers. We got his odometers switched from PID 245 to PID 244 (DDEC II) and it seemed to work fine. With the VMS 120, that would be a program change. I would have thought they made that change when you sent it back.
The above might address the mileage issues, but I think you have more problems than that. I do not carry the VMS120 in stock. I would bet that Martin would be more than willing to send you a replacement to see if that would solve the problems. If you do that, make sure that they program it for the '92 DDEC II option.
Sorry, don't have any better options.