Jonny, this sounds more like an intermittent contact in the lamp's power supply. I assume that these 'bulbs' are in fact light emitting diodes (LED) rather than incandescent lamps. As such they should last forever and a bit. If I am right, there will not be a large difference in brightness if one has to change it. However, most LEDs are soldered directly onto a printed circuit board, which can make the repair more difficult. Apart from taking the cluster out and gaining access to the insides, I don't think there is much you can do. With the cluster apart, look for a poor connection, or corroded plug/socket pins. Look for a forum member who has already serviced a cluster, and ask him/her about the assembly of lights/plugs etc, for guidence. Good luck