2020 GMC Canyon Power Train

The main issue is the transmission... It shudders. Now I have to change the oil every 10K miles on it, or it will start shuddering again. It first started when the truck had 50K or a little more miles in it. The issue was resolved, I thought... Then it did it again at 69K (Just out of the warranty). I called the dealership and they stated I had to pay if I wanted an oil change, and they could not do an oil flush even if I paid for it. So I said OK, I will take it to a mechanic, and I did and "fixed" the problem. I used the oil GM recommended and the shuddering stopped. BUT then, another 10K miles and it starts again. I have changed the oil a lot of times... It now has 128K miles in it, and this last time, I had to change the oil at 9k miles because of the shuddering... What will be next? I will have to change it at 5K miles, just like the motor oil? It is sad to see all these people having the same issue as I do, and GM does not do anything about it. I've done a lot of research... There is a guy that fixes the issue eliminating a specific valve, in the transmission, and updating the other ones with higher quality valves they make to fix the problem. I'm sure it would cost GM some money, but these trucks are expensive, you know? It is sad that no one is trying to help consumers when companies sale these cars and trucks to the public for a very high price and they do not take care of the mistakes they make when producing them. Please help us making GM fix this transmission issues. It is not fare for us consumers to be having trouble with new vehicles. Thank you for your time.

I AM THE OWNER OF A 2020 CANYON SLE THAT WAS PURCHASED IN JUNE OF 2020. THE VEHICLE HAS ABOUT 20,000 MILE ON IT CURRENTLY. I HAVE BEEN EXPERIENCING A "LAG" ON ACCELERATION AFTER COMING TO A STOP. THIS FEELS LIKE THE TRANSMISSION ISN'T DOWN SHIFTING ALL THE WAY. AT TIME WHEN ACCELERATING FROM A STOP THE TRUCK WILL ACT AS IT IS IN A HIGH GEAR THEN SUDDENLY SLAM INTO A FIRST GEAR. I HAVE TAKE MY TRUCK TO JESSUP GMC IN PALM SPRINGS AND THEY SAY THE TECH CAN NOT REPRODUCE THE PROBLEM. THIS SOUNDS LIKE THE SAME ISSUE THE 2015-1019 MODELS HAVE IN REFERENCE TO BULLETIN: 18-NA-355 DATED AUGUST 2019