If I happen to powerdown my Elite box to cause a reboot, then it boots back up with the LNB frequency having changed on AMC 21. Consequently, I always have to change it back to the correct value (universal to 10750). If I scroll through my satellite list I do not see any other corrupted values. Does anybody have an idea for a quick fix? The only thing that I can think of is to delete AMC 21 and re-enter all the data again to see if it sticks OK which is not a quick fix.
Shouldn't take you very long to try that, and it's probably the quickest fix you'll find. I really think that more than AMC-21 is corrupted. I'm curious whether you have the BIG sat list with both eastern and western sats, or have you been able to edit that list to get only the sats that you can see? Also, what firmware version are you using?
When I first got my Abox, the sat list was corrupted, and there was a sat at 1.0W that couldn't be deleted, and as long as that sat was there, strange things happened to other sats in the list, with parameters changing, etc. So if by chance you have an old firmware version with the sat list that is corrupted, you may be messed up with ALL your sats until you get that straightened out.
Anyway, if you DO have the BIG sat list, try deleting the 1.0W sat, and see what happens. If you can't delete it, I think your whole list is corrupted. I think with later firmware versions, you can delete that sat, so if you CAN delete it, then it may be easier to fix things.
Also, even if you CAN delete the 1.0W sat, I'm curious whether that sat re-appears upon the reboot. If that's the case, then it's possible that following the instructions in another thread for replacing the DVBS.dat backup file might solve your problem, however that could also cause even more problems, so if it were me, I think I'd get things working before doing that.
But basically, I think what is happening is that on reboot, the Azbox is sensing that something is corrupted, and it's replacing your DVBS.dat file with the backup file which does NOT have AMC21 in it's master list, so you then have the list of sats that you've saved channels to which DOES have AMC21, but it won't be able to retrieve LO and other parameters from the master list. Just my guess.