I messed with the 6changer in my F250 for a bit...then changed it to a unit with all bells and whistles plus a USB port (don't look back). AND I gained a nifty pocket/shelf to boot. When the GT's cd dies (coming soon) I'm ditching the whole kit and kaboodle for the same thing I have in the F250. My 2 cents.
Btw...did the installer put in your presets? If not, they should have cleared when power was disconnected----and a newly installed unit should have had no presets. Mine definitely cleared every time I unhooked it or disconnected the battery...your situation very strange as described.
Granddaughter says "hit W" wwwwwwwwww...she's learning to spell...wwwwwwwwwW. Cheers.