1997 Jaguar XK8 rear lighting causes error msgs

When I press my left blinker light, if I am applying the brake, it give erors msg 'rear light out' if I accelerate. The blinker works fine and the eroor light goes off. Periodically, other messages appear too and then dissabper at random.
I was told, by a mecahnic, that there is a ground problem in the left rear light panel and they need to adjust or place a ground wire in the panel to stop the problem. He said this will stop all of the random error msges too.
Question: have you heard of this before? Anc is this something I can do as a backyard mechanic. I can't find this issue anywhere.