2006 Mercedes S430 side view mirror indicator lights intermittently fail

What is your question?

The left and right mirror indicator lights intermittently stop working, one or the other or both at the same time and the “Mirror turn signal R / L, Check Light” warning appears on the dash. Both bulbs have been checked and work fine. No evident problems were seen in the side mirror assemblies. It’s particularly puzzling that both side mirror indicator lights are intermittently affected and then work again, but mostly they’re not working. At present, the left side is working normally and right side isn’t working.

What makes this problem better or worse?

I have found nothing that precipitates or reverses the problem.

How long has your 2006 Mercedes-Benz S430 had this problem?

Months. It may have first begun over a year ago and my mechanic replaced the L mirror bulb. But then it stopped working and then worked again. Of late, the periods in which it works are few and far between and the right started malfunctioning too.