Whether the amp lead is plugging into a standard jack socket or a barrel or end pin jack, the parts that grip the plug in place eventually wear. Most sockets have pieces of nickel plated brass metal contacts that are shaped to press against the plug “pin”. On a new socket the grip is quite strong and there will be a positive “click” as the plug goes in. Over time the constant wear on the contacts makes the springiness weaker until the plug makes a sloppy contact. You’ll first start to notice this when the amp crackles as you move around. By this time the usual solution is to bend the contacts, or in the case of a barrel style socket, replace the socket. Bending the contacts will eventually lead to a breakage.
The ideal solution is to replace the socket with one made of more durable materials, such as the ToneUp range of gold plated spring bronze jack sockets.