Good luck with it then. Only rationale I could possibly think of is he could say the stops on the aftermarket shifter were set wrong which didn't allow the transmission to fully engage and damaged something. IIRC the TKO line doesn't have internal stops like the 3650 does.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.