Are you certain the fluid wasn't overfilled? Also, a leaking transmission cooler can allow coolant to enter the unit.
When the vehicle is cool, check the condition of the transmission fluid. Make sure there is no indication that coolant is mixing with it. Also, let me know how much new fluid was added.
Next, there is a transaxle vent that could be plugged. I attached a pic below which shows a new one installed. You will need to remove the air filter box assembly to access it. In some cases, the shift linkage will block it as well.
Let me know what you find.
See pic below.
Tuesday, May 4th, 2021 AT 8:01 PM