I do not know if this applies to any of your situations but figured I would mention it.

A recently departed employee left a half finished project with dim dash lights. The entire gauge housing gauges etc. had been replaced. After verifying grounds, bypassing the switch and chasing my tail etc. I dug a bit deeper by taking the original apart.
The original cluster housing was molded out of white plastic and the entire inside was painted a bright florescent green.

The new one was molded out of black black plastic and completely black inside as well

I proceeded to do a bit of research und used Rustoleum flat white primer and their Fluorescent Green Spray Paint.
After reassembling the cluster the dash lights are now nice and bright with the recommended bulbs. IMAGINE THAT ? LOL