Troublesome Tahoe Transmission

My wife has 2004 Chevrolet Tahoe with 84000 miles on it. Transmission is slipping intermittently. It has been serviced on schedule including transmission. Trans failed in September. Mehanic showed me torqued input shaft with irregular hole in it. Mechanic rebuilt tranny. It seemed fine but a few days later, start car put in drive press accelerator, the engine revs, but the car doesn’t move (the brake is off.) Eventually the car goes. Take car back to mechanic. He finds no codes and cannot reproduce problem. Take car home and a few weeks later the problem reoccurs. Back to mechanic. No codes–cannot reproduce problem. A few weeks later reoccurs. Mechanic replaces transmission valve body. The car shifts smoother with new valve body, but a few weeks later the problem reoccurs. Back to mechanic still no codes and cannot reproduce the problem. Contact Chevrolet Customer assistance and they open a case, but cannot determing cause of problem. Any help or suggestions would be appreciated.

2WD or 4x4? Electronic dash mounted transfer case switch? Obvious question: all fluids up?

When they rebuilt the transmission, did they also replace the pump assy??? I would hope so if the input shaft was twisted. Either way, I’m betting there is something not right in the input drum or pump assy. Maybe a sticky regulator valve… I would have to go into it again after doing some pressure tests.