I have a Dish DVR 625 dual tuner receiver. Tuner 2 has very poor reception on some channels, but Tuner 1 is fine. It's not a cable problem - if I switch the input cables, Tuner 2 is still the one with poor reception. Anybody seen this before? I am told this model of receiver is known to have this problem, but nobody can tell me if there's a fix for it.