6-speed FW hub axles are poorly supported on the right side because the right hub bearings are so far inboard. Famous for breaking or bending (the stye of failure mostly dependent on axle steel quality. Cheap ones bend, better endure more, then break.)
You can look at the axle like a classic sophomore engineering beam. Supported with rigid "fixed" supports at each end - the dropouts. Loaded with point loads at each bearing with your weight and whatever you are doing to the wheel. (Slamming potholes, jumping curbs ...) The fixed ends provided by the dropouts help a lot. But ... if those dropouts are not parallel, they are adding another issue - bending moment. Bending moment is what breaks axles. The loads on the bearings create bending moment. Adding more with the dropouts makes it worse.
So - before you put a new 6-speed FW axle on your bike, take it to a shop and have them put the dropout tools on. Two cylinders with handles that slide into the dropouts like a hub. If the dropouts are perfect the two cylinders line up, If not, the handles can be tweaked to bend the dropout into alignment. Every steel bike gets this or should. And after the bike falls over or crashes to the right. Or if shifting is off. Or axles are bending/breaking. Aluminum - bend with caution. One moderate bend is probably OK. Two, and it will break down the road. Carbon fiber? Out of my element. That might be a warranty issue.