Dan Wesson cylinder/cylinder stop problem.

Recently, when rapidly firing double action, the cylinder will make an extra half turn with an individual trigger pull, as though the momentum of the turning cylinder is spinning it too fast for the cylinder stop to catch in one of the notches.
Is this the result of a weak cylinder stop spring?

Either that or the action is fouled up and gummy.

When the cylinder rotates past the cylinder stop, that condition is known as "Cylinder throw-by".
NOT good. You get off-center primer hits and worse, firing in an unlocked condition.

Fortunately, the one time it happened while I was shooting it struck the rim of the case and didn't fire. After it happened I tried to replicate it (and succeeded) with empty chambers, then snap caps.

Anyway, the action is clean as a whistle, so I probably just need a new cylinder stop spring.
Just my luck that's one of the spare parts I don't have on hand.