Heated rear window wiring

[Sol]

I don't have diagrams for the M59 to hand but the issue is probably a broken wire inside the rubber boot that links the tailgate to the body. Worth peeling it back and look for snapped cores. Join anything broken and that should solve it. Ideally best to solder or crimp and insulate the break.

With the flexing over the years, it's common for one or two wires to snap inside the flexible boot carrying the wiring for heated screen and wiper.