lose signal/picture sporatically - DirecTV DVR

For lose signal/picture sporatically, relating to DirecTV DVRs and receivers. We have 3 receivers and 1 receiver at times loses part of its signal/picture. I can have the same channel on the other receivers and this does not happen. I have changed the cable from the wall plate to the receiver to the tv and have changed what output post on the multi switch box the cable was originally on. This is very sporatic yet just started the past week or two. I did a self test and on satellite 101(A) signal was 84. I haven't replaced the cable from the multi switch box to the wall plate yet. I checked my internal connections and they all seem tight. I sprayed air duster inside the receiver just in case there was a dust build up and maybe creating a bad ground. When the picture breaks up it only lasts seconds then corrects itself. Any ideas or tips or suggestions would be greatly appreciated.