HingeJoint2D and DistanceJoint2D behaving like a spring?

I'm working on a 2D LibreScale ala:




The problem I'm seeing is with anchors at the top of each scale on the horizontal beam (where the triangle comes to a point). If a sprite with a rigidbody2d attached falls on them, the joints seem to behave more like a spring with the scale moving apart from the beam, downward and then "bouncing" back up. What might I be doing incorrectly? I've tried both the hinge and distance joints and see the same behavior with both.