8's:
The problem as I describe it would follow the Sony and would also still be present if you swapped wires at the LNB, but your description gives two results for these two things. I don't think he tried the same sort of thing with the Philips to see if it acted JUST like the Sony (but he didn't happen to do the same button pushes).

When I solved that problem at that house that I mentioned, one of the big bafflers was that one receiver was in the nursery, one in the living room, one in the office (different building), and each one was used for different channels. The problems appeared to be different from receiver to receiver. The answer only showed up when I tried exactly the same thing on each receiver and found that they all behaved identically.

And YUP ! The inline amp could be the source of the problem, especially if it somehow kept 18 volts from getting up to the LNB. You are right; he MUST test his setup by putting an F81 in place of the amp. That alone might fix it.

jfuex,
8's suggestion about where the amp is placed is really valid, too. If it is at the LNB, the amp will be receiving a signal too hot for it to amplify. That is like turning the volume up to 13 when you only have 10. If the amp really is needed, it should be placed far enough down the line (150 feet minimum) that the signal has decreased below the maximum that the amp can cleanly amplify. Again, if you remove the amp and ANY of the signal measurements increase, or even stay the same, then the amp is doing no good and could be making your signal problems worse. Fortunately, though, not actually hurting any gear.