I know it can fail, because it happen to me 2 times.
Pleaselog inorregisterto add a comment.
Critical Captures just perform oneshake checkinstead of 3, and those depend on the Pokemon’smodified catch ratewhich comes out of this formula:
HPmaxis the number of hit points the Pokémon has at full health,HPcurrentis the number of hit points the Pokémon has at the moment,rateis the catch rate of the Pokémon (which may be modified due to use of the Heavy Ball or actions in the Safari Zone),bonusballis the multiplier for the Poké Ball used, andbonusstatusis the multiplier for any status condition the Pokémon has (2 for sleep and freeze [2.5 in B/W & later games], 1.5 for paralyze, poison, or burn, and 1 otherwise).