i think this problem appeared only small object.
(object size in 3dsmax : Length 0.148, Width 0.229, Height0.471)
but my project must use little physics boxs.
first object set dummy.
second object set rigidbody.
and i set balljoint between two objects.
but second body scale changed zero.
and i can't changed other value(not zero).
i attached some screenshot, and used objects.