I had my 19 RST in the dealership today for this issue and I was directed to a Chevy bulletin that says this is a normal function of the transmission. Every morning I start my truck, put it in drive and go to leave my driveway and my transmission hangs up at the top of 1st and sometimes 2nd, and the shift is rather abrupt after the hang up. Apparently it’s caused by air in the clutch plate that purges over the first 2-3 upshifts. Chevy literally put in their bulletin that “no repair attempts shall be completed”. All they told me was it has everything to do with transmission temp and they way the POS 8 spd is to supposed to work. Sort of hard to believe that it’s normal but hey what can we do.