Replace the solenoid in question. 4-5 shift.
Or give lubegard some more time.
It usually takes 200-300kms before I really notice a difference after applying lubegard, in city driving with lots of shifting.
I already drove over 200KMs with Lubegard.
What I just did is - i have a "Launch" Scanner with me anyway - I did a live stream on a few solenoids and here are the screenshots.
The culprit is Shift Control Solenoid Valve C (35R/C) which is responsible for 2nd to 3rd AND 4th to 5th shifts. I am not quite sure if the voltage is within standard limits but it seems that this specific solenoid's voltage is the least of all. Paying close attention to its behavior, I felt the downshift from 3rd to 2nd being a bit harsh too.
Please take a look at the attached images. (check the legend under each diagram as the color code changes from one image to the other)
What do you think?