02 Protege5 AT upshifting at cruising speed


Mazda Protege5 2002 Sport Mazda6s wagon 2004
I have a bone stock 02 Protege5 with Auto in it. Cruising along happily for about a half hour.....between 40-50mph it starts searching for the right gear, up shift and then back, just happens randomly.

Any suggestions? Fluid full to mark and checking while warmed to operating temperature, pulled the electrical connectors and cleaned them, removing one at a time, cleaning and replace before moving on.

Car has 238k runs like a top, just this transmission thing....