I recently aquired an E61 2006. An error flashes up everytime its started showing rear bulb failure but the bulb is fine.
Any thoughts please?

it also randomly cut out without warning but started straight away. Was thinking both were related somehow.

 

I had that exact same problem. It could be due to a poor connection, faulty socket or wiring. Even though the bulb lights, it could be drawing too much current. Mine eventually resolved on its own after fidgeting around with the bulb.