Check the hand in the face of the breech and see if it has any spring tension on it.
The hand spring (at least on the post-war guns) is nothing but a short piece of piano wire attached directly to the hand in a small hole and crimped into place.
The wire/spring can get lazy after years of use allowing the hand to skip off of a ratchet tooth here and there leaving the cylinder out of time in no particular order.
Simple packed in dirt and oil accumulated in there will also stop it from functioning right and give you the same thing.
The hand is attached to and works off the motion of the trigger. If the fit between the hand and the trigger is excessive and sloppy, you can get timing problems.
The very tip of the hand that pokes through the window of the breech face may be worn. It's almost a sharp point when right as it gets under each ratchet tooth and lifts the cylinder upwards to rotate it..
They just plain get worn over from use like everything else can. Not the hardest metal part ever made either.
To rebuild a few of these, I used to cut the upper edge of the worn hand off and face it w/a tiny layer of steel from a power hacksaw blade. Silver soldered in place, quenched when the solder just set, it left the tip hard.Then draw it back a bit and refit.
Lots of work for one of these but there just weren't any parts available.
The last one I worked on was bought for $14.95 in a LGS 'cause the timing was off a little. It was a while ago.
Now they sell the hand w/spring attached for something like 10 or 15bucks... ! Must have been hiding the parts stash.
Check the ratchet teeth for wear. Many of the ratchet 'stars' are case (color) hardened but the wear thickness of the hardening is thin. If needed, you can carefully peen any obviously out of wack tooth back into position, reshape and polish it to match the others.
These revolvers use grips that you can change with the single screw through the bottom . They had 6 or 7 different styles to choose from.
The grip styles and the interchangable system was the work of some guy named Roper IIRC.