hello there, Helmuth.

since the issue comes up and goes, and especially when you hit a pothole, i would suspect that there is a contact issue... because you had the light burnt, and then the other burnt, and after replacing, they burnt again (or, just work intermittently), I would suspect some rust on the contact, that increased the line impedance, and the LCM "compensated" for increased resistance by increasing the voltage (actually, changing the PMW signal), which in turn shortened the life of the bulbs and finally just killing the bulb...

There are two places to look for the rusty or loose contacts - one is obviously at the bulb... since the area where the bulbs are is exposed to elements to some extend, rust can be a prime suspect...

the other area would be to look around the LCM - while the LCM is well protected in the right front passenger's footwell area, some of the sunroof drainage lines go in that area and may clog and therefore create some wet spots... usually in this case, you might have more than just one light problem but still, you might look into this...

keep us posted, good luck...