I've found that the rivet connecting the "button-like" attachment mechanism is now slipping, causing the arm to fall down. The weighting suggestion you make will not solve the problem. It's a mechanical failure not a weight issue. The rivet should hold the button to the arm in an immobile fashion, using friction between the button and the red isolating plastic piece to stabilize the arm. That connection has broken, so the solution seems to be finding a way to firmly attach the button and the arm, e.g. glue or weld.
Los Altos Tizio User, October 2012