Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, the only easy user doable / proposed preliminary tries (if have not been done):
These would serve as both an attempt of a fix and as a test by process of elimination. If not corrective, then it would point to an internal hardware issue.
If comfortably able and feel safe to do so, are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter and even a soldering iron? It would help to likewise have access to a signal generator, scope and dummy load with wattmeter.