The most common picture: a plug of lint
Your phone sits in your pocket every day, with the charging port pointing down or to the side. Textile fibres collect there and get pushed further back every time you plug in the cable.
Over time, a firm, matted plug forms at the bottom of the port. The connector no longer goes all the way in, and the contact becomes unreliable.
This happens slowly, over months. That is exactly why hardly anyone notices it until one day nothing works anymore.
