ongoing neck problem (S470DX)

hi guys. ive had a problem for a while now, it first started when i had the arm holder on the ZR tightened to stop the wobble, that worked but gave me a horrible side effect, a dead-ish spot from around the fifth fret to the seventh on the g string the notes (Particularly the seventh fret) played, but did not sustain as long and had a choked/muffled sound. i suppose the neck warped or moved while the tention of the strings was relaxed. i got used to it.

Just resently i had a dimarzio X2N installed (sounds great) and of course all of the strings had to be taken off during the process. after it was put in i went home and changed the strings, same gauge, same brand (D'addario 9-46) after i tuned up and stretched the strings i noticed a dead note, its the 14th fret on the g string. it plays and makes a horible choking sounds and rings for only around a second or two. I am quite certain that it is the frets rattling. But my question is why is it warping each time i release some tention? is there something i could do with the truss rod to stop these unwanted shifts?

I suppose ill be getting a fret dress some time later but i need to know this isnt going to happen again and strip me of $90 they carge for a fret dress.

thanks, Jarrad