I've noticed a couple of times lately that my Square Four side stand spring has become detached from the stand, leaving the stand swinging in the breeze and ready to throw me off on the next left hander. This is the 2450-48 & 2450-50 short side stand fitted to 1948-52 bikes.
I've retained the spring with a tie wrap. Hopefully this will sort it out. The stand is still free to move. but the location of the spring is now controlled so that the spring cannot pop out from under the stud.