I had this issue, they also said it was the sunlight. GM has created a software update to fix this issue. It's free and the dealer can do it in a matter of minutes. I took mine in and its running great now. Hope that helps!
2016 1SS 6.2L LT1 Manual 6-Speed
, Front Emblem Blackout, Rear Bowtie Delete, Phastek Side Marker Tint, GM Black Taillights