I spent several hours last night searching for the authoritative version of what I said earlier. I fell asleep.
This is all I'm suggesting and the reason. Some cylinders have longer spigots or some cranks have bigger throws. Not sure which is the case but it's vintage dependent, or, only happens if x vintage crank is used with y vintage cylinder. So dry fit the parts and check the clearance of the crank to the cylinder spigots as the crank rotates. If the crank hits or is very close, grind some notches at the offending place in the cylinder.
I have really heard this, that there can be a problem. There are many things that should often be dry fit anyway.
Your using the O-ring makes for a better assembly. It will leak less.