I get confused about terminology, so here's a diagram courtesy of Moss. What I was talking about was item 110. These washers have an inner collar that is supposed to deform to match the splines on the trunnion pin as you tighten the nut. (So the washer cannot turn on the pin in operation.) What I've heard from others is that the reproduction washers are much harder to deform than the originals were; and damage to the nut and/or pin ensues.
I'm not even certain the problem is the washers; could be that the splines on the pin don't have the same lead-in taper that the original ones did, which helped form the splines into the washer. But either way, reusing the old washers should solve the problem.