Update! Thought I should update this posting so you all know it was "user error"....well, not error, as much as misunderstanding the precipitating factors of the "catch". I discovered it clicks like that when I've reduced my presser foot pressure to 0, which I was doing when sewing on those thick bindings. I put the pressure back to it's usual position and it doesn't click anymore. When the pressure is so low, there must be a looser part inside that will move around freely, thus clicking would occur sporatically. Thanks for all of your help everyone!