CLK Cabriolet -- Mirror Question

2003 CLK Cab
Passenger side mirror.
Drops down for backing up, but when it goes back to its programmed "normal" position, it doesn't go all the way back out. It comes up, but not all the
way out. Over time, it creeps further and further in.
1st visit, the dealer said it was a memory problem and replaced some chips. I knew this wasn't the case, since to get it back to the proper position all I needed to do was push the proper memory button -- it knew where to go, it just wasn't getting there.
2nd visit -- they replaced the motor and controller on the mirror. Unfortunately, this didn't fix it either.
3rd visit -- no idea what the problem is -- the Service Bulletin for the C-Class for the same problem has them replace the controller, and they've already done that. Per the Service Advisor, "How big an issue is this for you?"
Anyone have any insights?

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