Tongue of 1972 Shasta very difficult to get off ball.

Small point, it called a coupler instead of tongue. Now that I have proved myself to be a dweeb let me offer more positive input. I have two of those couplers and they are a bear to release if there is any pressure against the clasp. While I have never needed to, isn't there a nut up under there that adjusts clasp grip? I am sure clasp in the wrong term but works for me.