motion study and contact problem

Hi,

im doing a motion study analysis where, there are 3 - 4 motors in one assembly. i run the motion study step by step, from 1 motor to 2 motors sequenly. i also define a contact between the parts, so that it will not pass through which is not possible. initially it was ok ( the part hitting each other) but when i added another motor to other part, the previous motion which was ok earlier now seem impossible ( instead hitting each other, they can pass through) its like the contact i did previously is not working.

thank you in advance.

SolidworksMotion Studies