That’s a shame. I think most people will be fine with the screw as long as they keep it dry but I wonder how common it is to have it snap off.My first R41 could have lasted 50 years as well, but yeah, the cap broke away.
I got a replacement head from Mühle for free, though.
I think the newer 41 and 89s have plated brass screws? Not sure if that makes much of a difference since they can still snap off.
They ought to just make the whole top cap out of plated brass to be safe and I doubt it would cost much more.