There’s two things that could get it acting right that I can think of: Replace the cylinder (expensive, may not work but might) Shim it i.e. find a washer with internal diameter of cylinder pin or smaller and rut it out to the right diameter, then file it down to the width that takes the play out ( couple issues with this, one it’ll increase the flash gap i.e. bigger halos, reduced velocity and increased leading, two potential annealing of the makeshift shim with the fram of the gun) Let us know how it goes

Seconding this one. Looking at the furthest from camera case, my money it that there is play in the cylinder along the axis of the cylinder pin. That case being swollen, just above the rim means one thing, that the case has enough room to move back out of the cylinder while firing to allow that to happen. Overpressure i.e. hot loads may be contributing to an issue you wouldn’t observe with lighter loads. Have you played around using different ammo?

“la forma de la nalga”