Alfa Romeo Spider 3.2V6 P2099 - Lambda sensor upstream bank 2 (feasibility)

[alfabertone]

I'm having the error in the subject on my 939 3.2 V6, although my upstream (pre-cat) signals are ok.
One of the downstream sensors had a very low signal and also the integrator of bank 2 was always 1.
Leaving me with one of the cats for bank 2 or the down stream sensor (although the code says upstream sensor)
Since I want it to be right I started with replacing the downstream sensors.
For a while it looked good but the error returns.
I can not find anything wrong on my pre-cat signals. Are we sure the comment for code P2099 is correct. Or the signals are not swapped.
Every help is highly appreciated.

P2099 is normally Bank2, Lambdacorrection post cat rich limit exceeded
This should be a general issue

regards
Arthur