Warped Neck on my 2005 Erie Ball Stingray V

I purchased this bass used and although it seemed to play quite nicely and has great tone, I restrung it with flatwounds and attempted to lower the action. That is when I noticed the slight warp or curve in the neck of my bass.It is not twisted but rather bows at the neck and there is no adjusting it out. The best I could do was to lightly sand the frets closest to the pickups to get the action close to where I want it but the is still a bit of fret noise off the first frets. Anyone else have this occur? Pretty expensive bass to have this flaw. 😡