Need a tranny pro,its crazy

[Blkt6]

Had the tranny rebuilt w a new torque conv. also from a very reputable shop.He came higly recomended by other gn owners and shops.The set up ran great for about 5 months then while driving normal in 3rd something would catch and slow the car down then release.no noises could be heard.problem contuined to get worse and woulnt release till it killed 3rd gear band.The shop repaired it.About 2 weeks after same problem and killed 2 gear band.The shop reaired it again.Now the car feels like it drags alittle,slower accel and to them the car drives fine and is fast,but i know my car it has much better bottom end and spped than that.Well 2 days later the origanal problem pop up again.Before i take it back again,WHAT ARE THEY MISSING!,can it be the conv,the tccselonoid was replaced last time.