I acquired a 2017 Cadillac CT6 in May 2019. The vehicle arrived with only 10,000 miles. Everything worked perfectly and the car was truly a pleasure to drive. In June 2021, I noticed what seemed like a shudder while accelerating. It was a one-time occurrence so I didn't think too much of it. Over the next few weeks the shuddering began to increase in frequency of occurrence. It is now Sep 2021 with 30,000 miles and the shuddering now occurs each time the car is driven. A tap of the accelerator usually clears up the shudder at that moment but it occurs again as the car accelerates. GM Technical Service Bulletin No. 18-NA-355 dated August 2019 appears to address the issue. This TSB calls for a flush of the transmission fluid. That service has not been performed on this vehicle as yet. This service as reported by other owners would seem to suggest that this is only a temporary 300-700 mile fix. Would love to hear other repair thoughts.