When my wife or I drives her 2017 cruze and the rpm's are 2k or less going down the road at a steady speed, sometimes the rpm's will suddenly shoot up to 4k rpm's without any increase in speed at all. It's almost like the transmission is slipping. No trouble codes, and when the oil was changed recently at the dealer I asked the dealer to check it out. It didn't do it for them (it doesn't do it for us all the time either) and they had no idea what it could be. After it starts you have to back off the gas pedal until it goes down, but of course that slows the car down and annoys the idiots behind you who are tailgating. It maybe happens once a day. (?) It doesn't seem to do it in start and stop traffic, or if it does it's not noticeable. Anyone have any idea what it could be?