2014 Dodge Ram 1500 shifts down hard when braking

Had the transmission worked on replaced torque converter right before I purchased truck. Got it back from shop and it shifts down hard when I’m braking or when I’m about to pass someone. Down shifts really hard passing. But shifts up and all normally. Took truck back to shop because it wasnt doing that before I took it in the first place. They said it needs to be flashed for the transmission bc something isnt right obviously. Ever heard of anything like that? And not sure if torque converter was all that was replaced.

Yes, transmissions are computer controlled.