4L60E intermittent harsh shifts

[87Skier]

I've been having some issues with my 4L60E in my 96 Suburban.

After it is warmed up, shutting it off for a short time (10 minutes to 1 hour), then restarting all shifts (P to D or R, 1-2, 2-3, 3-4) are very harsh. 2-3 and 3-4 are less noticeable.

If I wait longer than 1 hour or restart within a few minutes the transmission shifts into gear and between gears smoothly.

I cannot replicate the issue while driving alone. It only happens when it has been started hot after sitting.

The ECM isn't reporting any codes and the check engine light is not on. The speedometer works without issue. I checked and changed out the throttle position sensor because it had more play in it that I liked. I verified it's functionality with a OBD2 reader. I am unable to view the transmission temp through the scanner.

The transmission itself was used when I got, and I've put 60,000 miles on it since being installed in 2015.

I had a harsh shifting issue in 2017 that was due to the brake light switch being defective. The brake lights are still working.

Any ideas what to look at next?

Thanks for any help