It being an old Range Rover, you can probably take apart the window switches and clean the contacts up. And if it has a rear window cutout switch that often needs the same treatment.
My SD1 needed this periodically. Watch for pinging springs when you open them up.
Electrical contact cleaner spray was essentially a cure all for the 1992 Vogue we had when I was a kid. Still haven't forgiven my old man for selling it before I got my driving license.
It had a Mazda 35slt engine swap with a big turbo and limited slip diff on the rear. Absolute beast.
It being an old Range Rover, you can probably take apart the window switches and clean the contacts up. And if it has a rear window cutout switch that often needs the same treatment.
My SD1 needed this periodically. Watch for pinging springs when you open them up.