Sims cannot produce acceleration. Human body apart from visual cues experiences g loads which cannot be simulated. As a result there is a mismatch between visual cues and sensation (which is absent). That triggers symptoms like having eaten a poisonous substance. I have seen a captain throwing up in Sim. However I find A320 sim fairly OK in crosswind landings and EFATO. In Airbus nothing much happens with engine failure so may be easier to simulate.