If that has not been the normal shifting, then I can surmise you do have some varnish formed in the valve body and on the servos. Doing the pan service will be a start to clean them up. But you may need to repeat at least fluid changes a couple times at 5-7 miles intervals. You should see some improvement after the pan service within a few hundred miles. When the pan is off you can use WD40 spray liberally on the expose valve body and wiping off with a clean white rag. Make sure you meticulously clean the magnet and the pan. You do not need to use sealer gasket only but follow a stepped sequence when tightening the fasteners and recheck a day or so after before you reinstall the plastic chassis cover.
I am actually getting to read to do my 5k servicing which is changing the fluid only in the trans pan myself. But not this week end it is to fricken cold in the garage or shop right now . The garage is warmer at 52F but I am not into working in the cold anymore.... LOL