I have been experiencing bad shifting and when I decided to dismantle the whole thing, I realized that the rear derailleur was not providing enough tension so it could not go back to fully retracted position just as if the spring was not working correctly. I decided to open the tension bearings cage and re-greased the spring as well as the bearings and made sure everything was in place but no improvement.
I have uploaded a Video with the described issue here:
I hope there is a fix for this. I would not want to dispose such an expensive piece of gear.