What is the end result of the check switch? Does it show 4 ports, with one satellite listed twice and all say "ok"? I have run into this a few times. After replacing everything else, I blame it on an electrical wiring problem within the house. A few times I have seen where one room will show that symptom, the rest of the rooms in the house are fine, and when I run an extension cord from a different room on a different breaker to the problem box the problem disappears. Only once have I seen a whole house setup with 4 tuners do this, and I never could fix it. As far as I could tell, even though I knew something was up, it did not appear to affect the function of the system.