I was told that too about my 96. It never went up or down, always stayed down. However when I manually pulled it up, my radio all of the sudden got great reception. I would have to think the rear window defroster would interfere with an antenna crossing it like that.

__________________
1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"