2020 tacoma TRD hard shift into Reverse...sometimes

My 2020 TRD off-road is acting strange.
When going into reverse the automatic transmission has about a 3-second delay and then hits hard. Transmission shifts fine going from park to drive or neutral to drive and shifts perfectly. The shifting indicator light on the dash will not light up but the gear shift does light up going into reverse, but does work for park, neutral and drive, also the backup camera and reverse lights do seem to work. With all this going on it shows no transmission codes. I had the transmission fluid flushed and replaced and the mechanic said there was "normal wear" of the fluid but fluid was discolored. He said if it continues it is most likely the transmission. Seems odd it would be the transmission but maybe that's just cause I don't want to go that route. 55k miles on this vehicle.
If anyone has had something like this going on with their truck, I could sure use the advice.