Please add phase tracker to the application and check what phases of lifecycle have been executed.
I am sorry,
I added the phase tracker and saw that everything works fine. It was skipping UPDATE_MODEL_VALUES because the converter was raising an exception and I forgot to add to rerender the error messages (h:messages) in the a:commandButton.
My bad, I am ashamed, the a:command is working fine. This discussion can be deleted if possible.
Np at all - glad it's working now