It sounds like it is the memory line that is giving you the headache. I believe that line of power cannot be disconnected by any way other than physically disconnecting the wire itself. I don't want to be quoted but I believe it is a yellow wire. If everything is off, including disconnects, is it possible for you to check the yellow wire for power ? Obviously the downside to killing that power is that you lose all the data you put into the radios memory.
If you have friends who make you laugh, spend lots of time with them.
2008 Winnebago Sightseer 30B