I have close to the same issue . Mine fluctuates between hot and cold . so I am constantly either raising or lowering the temps . I have a 2016 3500 and none of these issues . New PW ( 2019 ) and always changing temp . Total PITA . Driving from Florida to Md and I'll put at 72 , then it becomes blazing hot , so have to put it down , then vice versa . Unacceptable on a 65k truck . I dont trust my dealer at all , they try to treat me like an idiot . I took in 3500 for service , pick up truck they had broke the attachment for my Amp steps , so I had to order another cable ( 100$ ) , then my light bar wouldnt work . I was told that was because my rear cab light was out ( have a cap , so dont need to fix it ) . I explained it was hard wired and not integrated into the system . I took my truck home fixed both , I guess I need to find a reputable stealership .
Sorry for the rant , just hate having an older truck with 100k miles run like a top and less then 1 month old truck have minor issues hehe .