Same problem - have had 2 dashes replaced
I have the exact same problem - hot Texas sun.
I first noticed in cold weather, when I ran with top down, full heater blowing over the thin leather strip b elow the vents.
Dealer has replaced dash 2 times (I am on my third dash part, same problem keeps coming up).
I have reported to Chevy, have a case number from their customer support/product quality division. I will keep replacing dash until I get resolution. It's a REAL PAIN to sit in a dealer's office for 2 hours while they replace it, but no option!!!!
I hope they manufacture a part that fixes the problem, but your pics could have been a photo of my dash - EXACT EXACT EXACT same problem.
Report your problem to Chevy!! Maybe they will fix it.