Brian, check battery connections. Make sure they are clean and secure. Have a tech put a scan tool (Pro-link) on it to see if it's logging any codes. I usually "reset unadapted shifts" and "activate fast adaptive", then drive the vehicle.. This lets the ECU re-learn the shift points, almost like re-setting it. I use my Pro-link to do this. I see this condition on occasion ,after we have removed and installed another trans, or replaced an ECU (trans computer).Hope this might help you. Good luck.
Do you have and run in the economy shift mode? It makes the tranny shift less, but also makes it downshift more roughtly at times. My tranny too does that frim time to time, but it not been an issue.