Instrument Lights

Check your courtesy light switch? Mine sticks from time to time in my International.

 

What kind of truck is this, year, make model? Lots of different way to to wire lights, could be relays, could be a body controller. Hard to help when we don't know what you have.

 

I had similar things going on in a 07? Century. They came on in the middle of the night. I don't know if it ever got fixed. I was assigned to a Volvo then. It fixed the problem on my end.
I could imagine some moisture in the panel. But water has a small head and the electricity is invisible.

Have fun. Good luck.