Hi, I have the same problem. All the buttons on the right side didn't work, also lost my lower speaker. This is a hardware issue. There is a FCC connection loose inside. First time I fixed it in sony xperia care store. But after a mild impact, it happens again. I opened back plate, put the FCC back, hot glue it, seal the back plate back. Problem solved. I believe this is a design flaw.
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