Could just be the bulbs, there are lots of overdriven chinese junk leds about. Switch is On top of the gearbox, remove the intake hoses to access, you need a deep socket I think its 21mm or 22mm to remove. I've had two ducatos where the reverse switch was iffy and a new one didn't fix the issue, I ended up grinding a few mm off the brass base so that it fitted further into the box, problem solved.