I had a DP Dual LNBF that I was using on 129, but going into a DPP-44 instead of a DPP Twin. It went bad in less than 30 days and I had to replace it, and then all was back to normal.
My problem started with not being able to pick up the Denver HD Locals on a low transponder, I think it was 2. After playing around a little, it turned out the low transponders were not working at all, or sometimes would fluctuate between 0 and 40, while the higher transponders worked fine. However, sometimes when it lost the signals, I would hit various buttons and end up to a channel that I did not subscribe to and would get some sort of message that I was not authorized that channel - call Dish to subscribe.
I'm sure that if a DPP Twin went bad, that in some circumstances it could effect the signal from the DP Dual LNBF not getting to the receiver. However, I don't know if a malfunctioning DP Dual LNBF can cause a DPP Twin to act up or not.
Just something to think about.