I have a 721 receiver that the signal keeps weakening on Tuner 1 and sometimes going out altogether. I have different lines to use in the basement coming from the dish and replaced the cable that runs up through the floor to the receiver and also switching the Tuner 1 and Tuner 2 cables but nothing makes a difference. When I do the signal tests and switch tests everything shows its normal, but when watching Tuner 1 the picture doesn't stay consistent. Has the Tuner 1 signal in the receiver just gone bad or something? It makes no sense and drives me crazy that recordings don't come out right and you can't ever watch Tuner 1 it seems. Has anyone else had this problem? I'm ready to switch back to a 508 for the bedroom TV.