I'll have to remember that. I'm not using my 8100 much anymore, but that was one problem that was very annoying, particularly back when they had that PBS mux with about 9 channels on it. It would sometimes take half the afternoon to get all the channels scanned in for that mux.
Usually though, it seemed to be related to times when my signal was not real good. Back when I had a BUD that worked better on Ku than my Ku dish, I used to have to switch to the BUD, scan in the channel, then switch back to the Ku dish, and then I could watch them on the Ku dish.
But back then I tried everything I could think of, including reloading the firmware, and couldn't get all the channels to scan in on some muxes. Seems like with all the things I tried, that turning the power off would have been involved, but maybe not in the same way.
Anyway, I'll have to remember that if I ever crank up the 8100 again.