Thanks for the informative report.
I bought a 621-2 and the Ku LNB was dead either on arrival or after
installation (I of course don't know which). Can you imagine a case where the switch dying could kill the Ku band LNB?
Your description of the ground loop current to me suggests that a simple
grounding block for lightning protection is in some respects a bad idea. It seems there could be a better method for preventing the coax from conducting a lightning strike into the home without a low impedance ground connection.