Phoenix crank

[Bob Culver]

Roller damage other than rusting is unusual, unless something has wedged, which could cause spinning. If the cranks are not ground after nitriding the diameter could be out of tolerance. It is vital to avoid high heating and to retain the fatigue protecting thin nitride layer intact.
For those with patience I cannot see why the crank cannot be sleeved and the housing bored to take an inexpensive metric bearing.
Fully split skirt pistons had limited life on many makes. And most rapidly developed clearance to rival solid ones.