Run continuity check on all the wires, or just order a new loom/s from Dave Barton , he makes them all.
Chasing faults with the wiring all funked up is pointless.
I spent many a spare Sunday trying to fix globes and wires in my wagon as I was working long hours , 6 days , 3.5 hours from home in the country I had no time. I could have run two wires from brake switch and 12v back to the globes easily but didn't think of it.......
New wires.