I have the same problem with my 2019 edge built before Nov 2018
On a whim I thought of mixing it up and used S mode then went back to regular mode.
There was a marked improvement.
I also tried using my paddle shifter and got up to 8th gear, it has to be at approx. 2000rpm or greater to kick in.
My suspicion is it has to do with oil flow in the unit but that is my uninformed suspicion.
It's worth trying it.