[Snake]

That's not a bug. Plisfa's Masochism only works on basic hit to make it hit, ignoring the chance. (It's not a 100%, it's a pseudo-100%, it just ignores the Evade check) Now Snake Dancer dodges the damage done. So it 'hit' due to Plisfa, but Cobra dodged the damage after an Evasion check.

This could be changed to make Plisfa's Masochism reduce Evade to 0 while it's active, though. But that's a topic for Balance Fu.