Has anybody had any problems with advance trac on the 03 Navigator?

the advance trac in my nav turns on and off randomly during normal driving and seems to be related to a clunk that sounds like it comes from the transfer case. I've had the nav in the shop 4 times to fix it and they keep replacing computer modules but that hasnt fixed it yet. to top that off, other parts of the electrical system seem to be going nuts recently.... the rear lift gate doesnt have power, the car doesnt 'know' when doors are opened and so the radio stays on and the interior lights dont light up, the 4x4 selector switch doesnt work (but the 4 H and 4L lights on the dash blink) , the check suspension light comes on, and it seems like the car gets stuck in 4x4 sometimes because when you turn a corner at low speed there is vibrating and heavy steering.

It is crazy that the dealer cant figure out what is causing these major problems, so I was wondering if anybody here has any experience or ideas....

thanks