First thing(s) I do if a light goes wonky is to take it apart as much as practical and “give it a tune-up”.

Snug up all retaining rings, remove/clean/lube all O-rings, clean/lube all threads, clean/buff exposed ends of the tube, springs, etc., for better electrical contact, and so on.

Yours sounds like it might be a driver issue. Ain’t got an A6, so will defer to those who do.