Just to be clear. On the keypad pressing 5+7, then adjust with the arrow keys, then pressing F10 does not give you a message?
That is correct, Skuzzy. 5+7 (and 5+3), adjusting position, then F10, do not show a message and do not save. Using the alternate joystick methods work just fine. Judging by the lack of threads on this specific topic, I assume this is a small bug affecting a very small minority. Its up to the HTC team to figure out why my computer is such an oddball.

I hate to be redundant, but in order to clarify: 5+7/5+3 head positions will not save in any plane or ground vehicle. All other head positions work properly.
If HTC needs any information to recreate the problem, I would be happy give any information needed.