Rear window defroster wire short on '96 S320

Hello guys. I'm from the W163 forum (ML class) and I'm running a favor for a buddy of mine with his '96 S320.

He has purchased a used '96 S320 about a year ago and has had the rear window replaced twice in this period. On both occassions, one or more defroster wires (embedded inside the glass)have shorted out on the left side of the glass necessitating entire window replacement. As his signature-class warranty is about to expire, he's concerned about future costly replacements of this glass. Is this a common problem with this M.Y. S-class? Any help would be appreciated.