I have found that, despite bending the shanks with needlenose pliers, the cars seem to spontaneously uncouple more in the warmer months of the year.
My very low tech approach is to wrap a small rubber band around the coupler to augment the downward pressure of the spring that keeps the coupler coupled. My American Flyer uncouplers will still uncouple the cars when activated but the cars do not randomly uncouple when running.
Like Jerry, I don't uncouple passenger trains very often, usually only to add a "head end" car so this simple fix seem to be working fine for me.
Little Tommy
