Did anybody come across a problem with such freezing monsters before?
i think what you are seeing is the monster dieing, but instead of falling downl, the ragdoll freezes right away.
i got this to happen all the time with ragdolls BY using the push k/v in a damage definition. in every frame, i would spawn a small radiusDamage 200 units in front of me but without the damage. plus i could aim it with the mouse. it acted more like a forcefield or something.
it looked cool, until a ragdoll would freeze in mid air and just hang there.
i wonder if it had to do with the lack of collisions. maybe the physics engine could tell it was not touching anything so it halted the physics.