@Crazy Finn,
do you still have the tuners isolated from the pc-case?
I have had similar problems with my Cine S2 V6.5. I also bought it as bundle with Duo-Flex. My Interferences where on the Tuner 1 (Adapter 0) and time to time on Tuner 2 (Adapter 1). Disabing the first 2 tuners (build in) was solving the problem for me too. I switched my mainboard from GigaByte (H77) also to AsRock(z77) but without any change. I also switched the kernel for KVM from standard pass-trough (2.6.32) to VirtIO (3.10) (I run it virtualized). But the final sollution was, I got RMA and sent the card back to DigitalDevices. Yesterday it came back with the Base replaced(Duoflex is still the same) but in additionally, the put an Floppy power cable bridge inside, connecting both cards together (without external power supply anymore) so my CC errors are gone, but I don't know, if it is the new tuner card or the kind of powering the Duo-Flex now... guess it could be booth, since you have isolated for F-Connectors before.
-One more question, are you still patching your signal monitor on tvhe build or is it now working out of the box?-
Answered this myself.. its now out of the box.Just pulled 3.9.1358~g2746998, I love that, I love tvheadend, thx :) !!!