The output jack is easy to overlook because it is simple. Two wires, one nut, one place to plug in. But simple parts still fail.
A loose jack can spin inside the guitar and twist the wires until a solder joint cracks. The guitar may cut out only when the cable points a certain direction, or only when the player moves.
If the jack nut keeps coming loose, the answer is not just tightening it harder from the outside. Hold the jack correctly, inspect the wiring and fix the reason it keeps moving.