Dual LNB problems

[BadWithComputer]

I recently bought a Dual LNB and intalled it to our dish.Its quite a high quality one, and signal on some transponders has improved by 20%. But on the channel 4 transponder the signal slips at about 8pm GMT until 10pm, while the other transponders remain stronger than they where with the single LNB. I suppose it is possible i have nudged the dish, but before i start the arduous process of moving the dish, is there any other reason? I´ll give the skew of the LNB another try. That might do it. Any other ideas??