Sounds like a short or bad connection or a poor ground , ground faults are the most common and even the switch itself can cause such problems , pull it out check for any signs or the plug in harness wires melting or the switch itself for damages or melting signs etc.Check each bulb etc bec one could be faulty or try new bulbs in their place.
Hope that helps and best of luck.By the way check the grounds and switch first then pull the cluster out check it for bad connections or burnt signs on its circuit etc and check the clusters ground wires , plus its wiring etc.Check the fuse box and the fuse socket for melting signs etc and the wires running to it etc.
