Something wierd with dual DVBT tuners

[HiZ]

I have installed my second DVB-T tuner and it sems some muxes (groups of channels) are received by one card and some by the other. I get the No Signal Received message on some channels unless im recording another channel at the same time then they all work OK.
I have disabled the hardware and rebooted. Now I can receive some but not other services and this matches what I had with both cards in. I am trying a removal reboot and re=scan of it all again.

I have Nebula and Blackgold cards. Running Nebula 1.32 as latest 1.36 seems to prevent adding new channels as I found in my last buld and have also read about elsewhere.