WordNet sense 1 (dangerously unstable and unpredictable):

treacherous

WordNet sense 2 (involving or causing danger or risk; liable to hurt or harm):

dangerous

WordNet sense 3 (showing lack of care for consequences):

irresponsible

WordNet sense 4 (liable to be erroneous or misleading):

undependable

WordNet sense 5 (likely to fail or make errors):

fallible

WordNet sense 6 (not consistent or dependable):

uncertain