I am not a gunsmith and have never encountered the problem you display but logically there is likely a problem with the hand and/or the ratchets on the back of the cylinder.

I doubt it sheds any light but I wonder if you have the same problem with ammo or snap caps in the cylinders?

A close up picture of the ratchets on the back of the cylinder may shed some light on the problem.

Other more knowledgeable may be able to advise you on how to best check out the hand.

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Scoundrel & Ne'er-Do-Well