Hi there! I have a very strange and quirky problem. Upgraded my standard halogen W221 headlamps to top quality aftermarket xenon ones. No issues on the driver's side - works 100% all the time in any scenario (Auto on/off, etc). However, on the passenger side, when I drive the car for an hour plus in heavy traffic, the headlamp can sometimes fail to come on. Switching off the light switch on/off does not clear it. The only thing that does is turning the car off and leaving it to cool down for say 30 mins plus. Could I have a faulty SAM unit for the headlamp that needs replacing (maybe a dry solder joint that's failing when heat is being generated from the engine). I have by the way swapped the ballasts around and still the passenger headlamp fails so think this is nothing to do with the aftermarket kit, must be the W221. Any ideas? Thx!