One side of A/C blows hot

[Blue Tank]

This is the perfect compliment to the drivers seat heater that works unless it's really cold out.
'04 burb with the automatic climate control and good readings on the high and low side. Last year when it was really hot out the drivers side upper vents would go in to super hot mode occasionally. Typically this would happen on a very hot day, 85-90+. This year it's much more common and happens while the pass and rear vents blow cold. If you turn the hvac control off and then back on in a minute it will go hot again. If you come to a stop and turn the truck off and then fire it right back up it will normally blow cold for a while. I'm thinking it's probably one of the inside temp sensors, upper or lower, but wanted to see if somebody ran in to this before.