It sounds like you may have a partially plugged transmission filter or the cooler is partially clogged.
How dirty was the fluid? Also, was it low before he removed some? Is there any evidence of a transmission fluid leak?
Let me know that. Also, if the fluid was exceptionally dirty, I would first start by changing the fluid and filter. I attached the only picture I could find of the pan and filter. When this is being done, have the cooler lines disconnected and blow compressed through the cooler in both directions.
Let me know if this helps.
See pic below.
Image (Click to make bigger)
Sunday, November 19th, 2023 AT 9:15 PM