Can you operate a DVR (625) in Dual Mode on QAM system?

[Doug2a43]

I have a 625 DVR operating on a Primecast QAM system distributing Dishnetwork. When I got the system I was able to get it in the Dual Mode and was very happy for six months. They recently downloaded new software and have locked it in the Single mode and disabled the second output. Both tuners still work as in the Single Mode I have pic n pic but I have no intrest in pic n pic, I want it to operate in Dual Mode. Primecast tells me they lock it in Single Mode because it is not stable in Dual Mode on a QAM system. It was stable for the six months I had it in Dual Mode before they "upgraded" the software. I can get it in dual mode by switching the 625 to satellite mode but as soon as I reconnect the QAM boxes and scan for QAM transponders it reverts to Single Mode and is locked there. Is this really an issue of stability or is something else going on?