Absolutely bring it back, because I suspect they over or under filled it.The fluid was exchanged by running new fluid thru the system until all the old fluid was out, pumping it out through the xmission lines, no machines were used. I went to a well-regarded and recommended local shop. It didn't flare before the replacement, and shortly after replacement I had two or three instances of flare on the 2-3 shift, then all was fine until this trip. Fluid was Toyota's WS fluid. I would bring the car back to the same shop I used for the fluid exchange.
That kind of exchange doesn’t always replace the precise amount of fluid.
I had a shop do the same thing on my 4 Runner. Didn’t check the fluid level afterwards - a huge mistake. They overfilled it by 1 1/2 - 2 quarts.
Didn’t figure it out until the transmission overheated, fried the torque converter clutch, and puked out a bunch of fluid on the highway.
The truck was never the same after.
Don’t trust that the fluid level was done right. The shift flare suggests it was not.