I has kind of similar issue with same tranny. Took it to dealer and described problem w/o suggesting anything. They charged me for 1 hour "investigation" ($150)
Told me that they have not found issue ..but problem was indeed gone.
However, during that time they updated software (I checked )
No problem since (3 years?)
When I asked before how much is transmission software update (as I suspected that may help) - was told $360 or so.....