Scirocco Register

My Scirocco has developed another little quirk. It's an intermittent thing, but it'll usually decide midway through a journey to act up so that every time I put the high beams on, the rev counter stops working. The oil lights flashes once as the high beams come on, similar to when you start up the car. The blue high beam light also doesn't work when it's acting up too.

Any ideas? Is it something as simple as a fuse or am I going to have to trace tonnes of wiring to find a loose connection?

Check your earths, especially the main earth from the block to the coil. Sitting in Washington services with 5 members of the register.