This is the empty body of the Magic Bullet with the motor removed.

There are three white plastic posts inside, which slide down when the jar is attached. There is a spring at the bottom of each post to push it back up when the jar is removed.

The posts have tabs on the bottom, one of which engages with the micro-switch on the motor.

The posts can get jammed if some liquid spills inside the body, since it is impossible to clean the sliding area of the posts.

To remove the posts, the black plastic strip on the top edge of the body has to be removed.

Since the black strip is glued on to the body, the easiest way to get it free is to dip it in boiling water.

Wait for a few minutes and then pry it off. Keep pulling up hard all round the edge and it will come off with a bit of force.

Here is the body with the black strip and the three white posts. The springs at the end of the posts in my Bullet were all rusted off.