Thanks, guys, for your responses.
I really think my problem lies with the unit apparently remembering a preset tilt position. If I knew how, or if, there were some kind of hardware reset, something to erase ALL the owner-programmed settings, and restore the unit to it's out of the box configuration, I'd be OK.
The return for replacement idea is next. Got it from Crutchfield, so that shouldn't be a problem. I really wanted to get it working, so I wouldn't have to remove it.
Thanks again for your comments.