said by frdrizzt:
Well, happening on all 3 HD boxes & not SD boxes could indicate one of the following (in no particular order):
1) Issue with HD feed for channels. Not necessarily impacting all regions, but maybe leaving your local head end.
2) Issue on the particular frequency/frequencies that the channels are transmitted in. HD & SD would not travel at the same frequency so noise or bad levels on those individual frequencies (and not just on 603 MHz, which the box locks on)
3) Issue with in-home connection to that particular set of boxes. If they all pass through a common leg of a splitter, you can try replacing it if CV has not been inside the house (I know you mentioned they were outside working)
4) 3 bad boxes. Least likely solution, but not impossible.
Possibly others. I'm not an expert in this matter by any means.
#1 very possible
#2 makes sense to me as well.
#3 Not the case as one of the HD boxes goes to a different leg them the other two. And the one SD box that is not experiencing the problem is sharing a splitter with one of the HD boxes that is experiencing it.
#4 Highly unlikely as you said. They even replaced one of our 4300HD boxes that was experiencing it on one of the TV's with a Samsung box as per my request and its still happening on the Samsung box as well.