Thanks, MrFTAMan.

Everything is OK on the 920 and the commercial DCII box that shares this dish.
If they're stuck on "H", that suggests they're getting 18 volts when they should get 13.
Have you checked with a meter?
Possibly a short or other fault in your switching?
(and of course the most likely problem IS a receiver setting)
Seems like there have been a few unexplained reports of odd behavior when connected to independent receivers.
I don't have enough facts to offer a clue.
Never understood the previous discussions.
But, I'd check the grounding of the different receivers.
In house-wiring where I live, you could have equipment in different rooms hooked to opposite phases of the 110vac line...

Could long cable runs and local lightning do something?
I'm grasping at straws.
But, if I valued my spare C2, I would not throw it into the same situation that broke my first one.
AND, is you existing C2 actually broken?
Connect it to just one cable at a time, and test it.
Monitor the voltage fed to it, in real time.
I would test to see if maybe both receivers were damaged by an unexplained situation.
Not that it's proof of anything, but I don't recall anyone using a 2x4 or 4x4 multiswitch reporting any troubles like this.
Let us know what you find.