Quick update, unfortuneatly the rough downshifts have returned! everything was perfect for a few hundred miles after i reset the shift adaptations, but it seems like as soon as it stopped learning the shifts for the adaptation settings, the rough downshifts returned. Im at a loss... I did replace the aux battery as well which did not make any difference. Is it possible the TCU needs software updates? Why would it shift perfectly during the learning/adaptation period, and then go back to rough downshifts after?

The only thing left to do is to replace the old H7 starter battery, but again im not having any issues with it at all. From what ive read it wouldnt even be related to this issue, would it?

 

You should do all the obvious first then look at what is left that upsets your TCU.
Rough shifting has multiple causes. As you now realize fresh shift adaptations have not solved the root cause... back to square one.