6i80 locking on 2 to 3 shift

I have been struggling trying to get this sorted, I have an LSA with a modified 6l80 behind it. It generally feels fine, when I start the car, drive off, shifts 1 - 2 fine, then shifting 2 - 3 its like I have stamped on the brakes momentarily. After this it shifts fine. If I turn it off, start it and drive off again it does it again on the 2-3 shift. I have been extremely gentle with it because it doesnt feel healthy... I have been trying to get some help from the builders of the trans without much success, which is why I am posting here.
Could someone maybe have a look at the tune and see if there is anything glaring in it ? Any help would be very much appreciated.

Happy to pay for time, I would really like to get this sorted

Post your stock tune.

Russ Kemp

Hi Russ, the only tune i have is the one i posted in the first post.Attachment 95091 is the log of the change, this is very light on the gas, if i give it more than that it feels pretty violent.

Log shows you are in Pattern B, per your cal you are commanding the TCC in 2nd gear under Pattern B, and right around the shift speed for 2-3 per your log. I don't know if it is hydraulically possible to apply the TCC in 2nd, but you shouldn't. Also in your log it looks like the TCC pressure is ramping up at the same time you hit the 3-4 shift. I would put your data in the Bluecat transmission program and recalculate it for all patterns.