I have a set of Mavic CXP-22 laced to Cannondale Coda hubs (i believe just from the factory) they are pretty old, but now one of the spokes in the rear non drive side is loosing it's tension. I noticed it, tightened and re-trued it, and now it has no tension again. it's the same spoke because it's two up from the spoke with my wheel magnet.
How do I fix this? Do I need a new spoke? What might be causing it to just lose tension? Thanks.