W124 auto window clicks repeatedly when reaching bottom

[87tdwagen]

Hi All,
I've had an issue with the auto window down feature on my Cabrio that I'd like to get your input on. The window travels fine up/down, but when it reaches bottom it clicks repeatedly and wont stop unless I tip the switch. I can also replicate the sound by manually holding the down switch till tge window bottoms, then then clicking begins.

It sounds as if the worm gear in the motor was popping out of the tooth gear on the regulator. Operating the window with the inner panel and liner off, I can't see anything amiss. I dont see the reg gear moving, popping, nor do I see the motor moving in its mounts. Everything is tight, regulator mounts, motor mounts. The reg gear doesn’t look damaged, the teeth are sharp and clean.

Motor worm gear bad? I would have expected to see plastic dust, shreddings and certainly impact the window operation, but the window zips up and down fine with no delay nor odd noises.

Ideas?