It’s a fretted neck ? If so there may just be a slight chance, especially if it’s been refretted, that the frets may have been ‘forced’ into too narrow a fret slot for the tang width, the hidden part of the fret that seats into the fboard. Many luthiers superglue frets In now so as I say, there may be a slight chance the frets are forcing neck issues. I think there is only one way to check all this I’m afraid and that’s a pro refret job. Other than this by what you are saying, the neck wood itself may not be right.
I think early Warwick truss rods were double flat rods that only adjusted one way before the later dual action ones were readily available.