Hi,
I found part of the problem.
Looks like the lower trigger have some overtravel so the hammer is hitting the trigger group.
I put a piece of lead on the back of the trigger guard to stop futher movement and the revolver snapp the caps.
Just have to underestand the working.
As I can underestand it, the paw acting on the cylinder star stop further movements.

I just want to let you know.

Thanks
Martin