Should Mechanic have rebuilt tranny b4 checking the TCM

What is your question?

My Mechanic told me I needed a rebuilt transmission. 7 weeks after taking the truck to him and 2 rebuilds later, he now tells me the TCM is bad and wants another 1500. He is claming that the faulty TCM didnt show up when the codes were ran.They are holding my car for ransom. I called 2 nissan mechanics and the BAR in Culver city. They all agree he should have found the problem with the TCM first. But he wont budge. BTW after 3 of the 7 weeks of the car being in the shop, he called me and said your car is ready. I went to pick it up. I Drove it 100 yards and my heart sunk, it was acting the EXACT same way as when I 1st took it in 3 weeks b4. I asked him, did it ever need a trans rebuild? he was upset by my question. So he starts looking for the problem and rebuilds it again. Then the TCM call.