[mikehodgson]

Check for pocket lint or other debris in the socket. This exact thing was happening to me, a minute with a toothpick fixed it.

[TonyTrapp]

Will check, but it's unlikely since both the phone and cable only ever sit on this desk. It's a pure debugging device.

[pbalau]

Hot glue it in place? It's going to provide enough strength to keep the things attached, but still will be easy to remove if needed.