TCM replacement for a 6L80E

[First c10]

Hey guys
I started working on my sons 70 again with an LC9/6L80E trans. After the teams rebuild I started having a problem with the very first shift into second each time I start the truck and put into drive. As I reach the shift speed it would like shift into 2nd or maybe even reverse really really hard for a second and then not do it again until I shut the truck off and restarted it then try and drive it again. After the first time it doesn’t do it again and runs/shifts normal. I talked to Mike at Century Transmission which is where I got the rebuild parts and he told me that the TCM may need to be re flashed from a GM dealer or someone with that capability. I took to a shop near me and he tried to reprogram with a new tune and it came back with an error stating it needed to be removed and reflashed on the bench.
Has anyone done this to a 6L80 trans TCM?
I thought I would just buy a rebuilt one but they say they need to be programmed. So I don’t want to buy a new one if I can just have mine reprogrammed.