Idiots got rid of the dipstick, quite a difference between checking the fluid level between hot and cold. If they check the fluid while hot, may even leak out leaving you short because they don't read the shop manual only to check it when its cold.
The thing has eight solenoid valves in it for shifting and torque converter lock up with a whole bunch of wires and switches between the ECM and the transmission. Even in the brake switch, one erratic connection anywhere can be the cause of your problem.
A kid had AT problems with his GM S10, least back then used a separate module for the AT, too expensive, jammed that into the ECM to save a couple of bucks, some of these are sealed, can't even open them up without breaking them. Did find poor soldering joints in his module, so call neutral safety switch was all corroded, polished that so I could see my smile, brake Switches also corroded,clean those as well as all the connector pins, both male and female. But first was checking all the solenoids for current draw and hearing that click, five as I recall, one for the torque converter lockup.
Nice was to spend a Saturday, forget about easy access, they don't give a darn about maintenance, buy a new one kind of thing. Didn't spend a dime for parts, added corrosion retardant, and was good for the next 100K miles until his body was a pile of rust.
Your guys found leaks? Did they repair them? Did they take your vehicle for a ride? Or did they take you for a ride?