Here is my theory. I suspect the problem is in the instrument panel/cluster. If the red wire with a white tracer to the IPC is getting power, the ground is good, and there are no loose wires on the battery or alternator, that is my first suspect.
Since you indicated the lights behind the speedo don't always work. To me, it sounds like there is a short in the cluster.
To determine if there is an issue in the IPC, body control module, engine control module, or the can-bus system, the vehicle should have the can-bus scanned for codes. CAN stands for controller area network. Basically, all computers/modules are tied together via a few wires. This scan type will identify codes regardless of the module storing them.
Here is a quick video showing how it's done:
This would be what I would suggest next. Otherwise, it will become a guessing game.
Let me know your thoughts. Also, if I don't hear from you for a couple of days, have a Happy Thanksgiving.
Wednesday, November 24th, 2021 AT 9:56 PM