It is either a computer controller issue of a problem inside the transmission itself. If i was facing this, I would change the fluid and filter, and then swap in an aftermarket stand-alone controller in. They are not cheap, but you get what you pay for. Here's one example.
https://www.usshift.com/usq4.shtmlIf there are still problems with the shifting, you may want to have your transmission rebuilt by a quality transmission shop who specializes in 4L60's or just buy another transmission outright. Trying to order and swap in a valve body in the car may help, but it may not either. Such is the nature of our hobby.
