100% to all the comments talking about lint/dirt in the usb port socket itself. I've had exactly the same problems, and 10 minutes spent cleaning out the port

100% to all the comments talking about lint/dirt in the usb port socket itself. I've had exactly the same problems, and 10 minutes spent cleaning out the port with a small toothpick or similar works wonders. Problem disappears instantly. There should be a USB FAQ about this with every product sold.