If you fail the smaller test gauge this means that your contact spring is too long. Twist the contact spring a rotation or two up the post.

If you fail the larger test gauge, this means that your contact spring is too short. Gently stretch the spring, or replace it entirely.

To remove the contact spring, pull it off the post. The post is the small threaded cylinder sticking out from the tip.

Twist a new spring onto the post while applying pressure. Make sure your new spring catches on the grooves of the post.