When you hook up your scantool, see if you can monitor the tranny fluid temp sensors output, that handyman was referring to.

If so, drive it 15 miles or so, to warm it up good & see what the sensor reports the temperature as, while your monitoring other things & witing for it to drop out of OD.

When it does, do the capture thing, so the scan tool will store all the parameters it's monitoring when it acts out. Then you can recall them for review after the drive.

Hopefully you'll get a meaningful code!!!!