What makes one wire "more flexible" than another? Did you switch to a thicker gauge wire? The wires look incredible flimsy to me. Some people have suggested putting a dot of hot glue or epoxy over the solder point. But in my case the wire broken in the middle. Obviously this is the result of repetitive strain (from a too short loop).

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I just checked and it was the same red wire on the aileron gimbal that broke. This time it broke a bit closer to the solder point.