my guess is that in first instance, imprision didn't block breakneck blizz from being selected, but once the other landorus used it, it was added to the moves that imprison was blocking.can someone help me understand this mechanic in z moves? not sure what happened: http://replay.pokemonshowdown.com/gen7pokebankou-481884397
if not glitch please help me understand
you could try to see if using imprison, then mimic to get one of the foe's move it starts blocking the mimicked move