Tvheadend

Hello,

I have a signal quality problem, not directly related to tvheadend (because same problem with vdr) but maybe is there someone here who can help me.
I have a PC with 2 pci DVB cards in it (1x technotrend S3200, 1x hvr-4000). The technotrend is working well and I have a good (100%) signal quality on almost every mux in dvb-S and in dvb-s2.
The problem is with the hvr-4000 (only using the dvb-s part, not the dvb-t) were I have a 100% signal on most of the mux, but on some dvb-s2 mux, I see the signal going from 100%, to 60%, 20%, even 0% then increasing again ... (with vdr, on that device, sometimes I had an image, but most of the time not). The dvb-s channels are working perfectly. The 2 cards are connected to 2 dishes by disecq switches, so normaly the signal they receives should be the same (except if problem in cable or switch).
I am using ubuntu 10.04, I first tried with the std v4l drivers, but there I had the same issues aswel on the S3200. Then I changed to the S2-Liplianin(from yavdr PPA)drivers, what did resolve my problem on the S3200 but not on the hvr-4000.
Is there an other driver to try, or something else to do?
many thanks,
SP