FWIW all Jazz Basses tend to have dead spots from the 4th to the 6th fret on the G string. It's possible the move to flats just made it more noticeable. I'm playing Pressure Wounds on mine and the 5th and 6th fret have pronounced dead spots. To me it's the nature of the beast. Some have added weight to the headstock to reduce it but I've never done it so I don't know whether that will help or not.
CV Jazz Bass/Wilde J45s, Matt Freeman PBass/Wilde P46, GK MB112 combo, tc electronic BG250 Combo.