Seems pretty self-explanatory, no matter what if a mob such as a dragon from ice and fire, a ghast from vanilla, or a warg from lycanites is able to move/be knocked back it will not receive the crit from the special attack of the dagger, or the flurry of punches from the Knuckles. thus making the dagger and Knuckles somewhat useless against certain types of mobs. I think the issue is with mobs being able to move away after the initial strike, some mobs such as zombies don't, but the wither, dragons from ice and fire, or wargs from lycanites will for instance. it's not just flying mobs either as the issue persists with the cyclops from IAF as well

hope there is a way to fix this or to add the original items to the config list to disable impact for the dagger to fix the knockback issue :)