Electrical Advice Needed

Sounds to me like your cluster "ground" might not be grounding. Also take the dash dimmer control, and in the dark, rotate it vigourously left to right to scrub the wiper clean. You may find it has a/ some "bad spots" where it doesnt make connection. For testing, you can clip a test lamp to the INST fuse. This fuse will be on one end of the fuse box

This fuse comes FROM the dash dimmer control on the road to the dash lights. You can use it for a "monitor" to see if it still lights when you lose the dash lamps

You will only have power on that INST fuse when the tail lamps are on and working, and when the dash dimmer is rotated far enough left to give it some "juice"