FreeBean

I had the same thing happen to me.
Anyway, I had problems with the NAV unit losing location & also bad reads; I had 2 different disks that were bad .
Inserted 3'rd disk I had, & NAV actually figured out my location without me telling it.
If you can't get the unit it to eject, take off the faceplate on the trunk mounted drive unit (5 EZ to push tabs), manually push in the 2 micro-switches, & EJECT it will.
The slide switch must not be pushing correctly what it should be. . Also, I'd like to remind anyone that it can't reject without power, so remember to have the key on Acc.

KING

iTrader: (1)

I think there is a way to re-calibrate the GPS system.
From your symptoms, a jumping location might point in that direction.