ASTRA 'F' SERIES TAIL LIGHTS - Andrew Scott

I own a 1993 Astra GLS, which has developed an appetite for Tail Light Bulbs.
The bulbs on both sides turn black after 1 months use (Heavy Use in Winter) and eventually fail.
I experienced this in a Company Astra(1992 Model) of the same vintage a few years ago, if I remember correctly the main dealer after a lot of headscatching
remade all the earth contacts at the back of the car, which then cured the fault.

Has anyone else experienced this problem, and where do I remake the earth contacts?