Help! 2020 Ford Ranger jerking and kicking while driving

It's XLT four wheel drive. The jerking started last summer. I wasn't paying attention until my friends pointed it out and suggested it might be a start of transmission problems. The jerking isn't that strong, just as if something is loose in the drivetrain and it's rather unpleasant driving experience. It mostly happens at lower speeds, rarely on the freeway. Since the truck is still under warranty, I took it to the Ford service center. They checked it agreed the problem is real and the transmission calls for an overhaul. So they took the transmission apart but it turned out some small part needed a replacement and it was on the back order indefinitely, so they just replaced the transmission with a new one. The jerking has not disappeared, however. I took the truck back to the center, they kept it for a week and said they can't locate the source of the problem, perhaps the new transmission needs to break-in, so come back after 3000-5000 miles. Which doesn't make much sense to me because the symptoms have not changed, no matter what transmission is in, old or new. And after 3000 miles the truck will be past the warranty range. Have other Ranger owners experience this problem? Was it fixed? And what other reasons, short of transmission, could be the problem here?