1.Check whether the headphone port is relatively loose. Pull out and try again to plug in the slot.
2. Use another headphone and check whether problem resolved, If issue resolved after change headphone, it's headphone's problem.
3. If problem still exist, it is suggested to back up the important information and restore the factory settings, plug again after restart.
4. If the problem can’t be solved, it is suggested to send it to the local after-sales center for inspection.
Does it help?