Installed the mod PCB and ground cable recomended for this issue but no continuity between the rear cover screw and the DP was detected. Took the left hinge apart and found that the ground spring that was supposed to contact the hinge shaft wasn't touching it. Bending the spring and a little conductive grease helped but will probably replace the hinge and maybe add a ground strap to be sure.

I had this problem and I replase Dp cabel problem was solved.