Neck still backbowed?

While setting the action on my bass (douglas WOB-826 fretless), I noticed that the neck was backbowed, and no matter how much I loosened the truss rods, the neck was still in a backbow. Somehow, I think the nut broke loose on each truss rod when a tech was trying to adjust them before, and I never noticed until now, but is there anything I can do about this, anything further I can check, or should I just suck it up and get a new neck? Any advice is appreciated. Thanks!

[Hellbastard]

Do the nuts come off the truss rod channel?
First you should chack if the TR thread is broken, then what I would do would be without tightening the TR clamp the neck and try to force it back to relief and start working from there.

The nuts still appear to be on their tracks, as I can tighten the truss rods and the neck backbows even further. Frustrating.

Non issue now, parts in question are being replaced.