REPLACE THE DIPLEXORS, THEY AREN'T CABLE SPLITTERS, THEY ARE CHEAP LIKE ALL SATELLITE EQUIPMENT, IF I COULD YELL AT YOU RIGHT NOW I WOULD! seriously, they are cheap and if everything else is right, then you ought to be able to replace one of the diplexors, if it for some reason is shorting then you will have squat for sat and probably a crap pic on the cable
This is CABL.com posting #180640. Tiny Link: cabl.co/mU9I