Hi,
It may be that the 3.5mm socket has either a dry solder joint connection on the motherboard, has become slightly loose on the board due to removal / insertion of plug over a period of time or the internal springs in the socket which connect to the plug have lost tension.
In any event the controller will have to be opened for the problem to be diagnosed and repaired.
Here is a link to a video which shows the disassembly of your controller. If you stop the video at 2:15 minutes you can see the socket (I think- not sure if left or right component) on the circuit board, (on the board at the back, in the area just above the USB socket on the front board in the picture). Looking at the picture I cannot tell if it is a surface mounted or a through hole soldered type, so you will have to determine the problem once you get it open. Test if the socket is loose, by very gently trying to move it. It should be not moving at all, if it does 'rock' the connection is loose and will have to be remade. If the connection is solid the socket will have to be replaced as it cannot be repaired.
https://www.youtube.com/watch?v=VJ3qnxTielA