according to PJ12's document the AP should not have disengaged only with an ADR Disagreement (and ALTN 2). It would take two ADR failures or two IR failures. Though in the Air Caraïbe sequence, you get the same ECAM FLR (and irreversible AP loss) from an ADR disagree only.
Jeff
PS) and similar problems (A/P, A/THR loss, ALTN, ADR Disagree) in... 1994:
see the documents published today at
Eurocockpit - Accueil