My thread on my shaky lights is here
I may have internal problems as well, but from the outside they don't exhibit the classic signs (unable to aim, pointing too low, wiggling the adjustments and bulb casing causes internal to flop around).
I can confirm that my entire assemblies move WAY too much in my pre-LCI sedan. I know there's a TSB but it seems to be coupe/conv only. From my teardowns so far, I can't believe it's designed this way - the light assemblies have almost zero support from the bottom which causes them to bounce around.
I feel this bouncing also causes the excess internal mechanism slop and damage. If the whole light weren't bouncing around so much, it wouldn't promote so much vibration and shaking inside of the assembly either.
E39s have chronic adjuster failures, and several aftermarket options exist which are made of superior materials. We need to get the E9x market going on this too. Perhaps we should approach some of the E39 part-makers to see if they'd make parts for other models. Of course E39 lights are a breeze to open (except for 2003s).
I don't want to go through ripping my lights open if I don't have replacement parts anyways. I'm going to continue working to see if I can stabilize my light housings in the chassis. I've followed and been followed by other pre-LCI and LCI E90 sedans and their lights don't shake even close to as much as mine on the same roads.