Hi Bug,Bug wrote: ↑Wed Feb 17, 2021 8:19 amHold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
Yes it's the 2 large screws that hold each rear cluster in place that have had bolts put in them.