The symptom
The guitar cut in and out when the cable moved. Sometimes it crackled. Sometimes the signal vanished entirely. That can be a jack, cable, solder joint, switch, pot or ground issue.
The diagnosis
The output jack is checked physically and electrically. Then the signal path is inspected for loose nuts, twisted wires, cold solder joints, dirty contacts and shielding or grounding problems.
The repair path
Sometimes the fix is a tightened jack and cleaned contact. Sometimes the jack needs replacement or the wiring needs to be re-soldered so the problem does not come back after the next gig.
The result
The guitar should pass signal reliably when the cable moves, the controls are touched and the instrument is played at normal stage volume.