Hi guys. I have some issues with my bass,Fender 70 Classic Jazz Bass. The first problem is that screws which are used to adjust inidividual string height are not fixing properly and are getting loose by themselves after about an hour of playing. And there are issues with adjusting intonation properly. Intonation is adjusted right but notes above twelth fret are slightly off pitch. If the truss rod is adjusted to straighten the neck a bit or strings are set a little bit lower, fret buzz appears and the instrument becomes unplayable. I prefer 120-60 gauge strings for drop C tuning. What would be Your suggestions for resolwing these issues?