For the meantime try mo: sa speaker settings turn center channel to none. then play a 5.1 or 7.1 movie track and check if the dialog is still garbled. if ok ang dialog, sa center amp ang sira. try mo ulit set to small ang center. pag garbled pa rin, sa digital domain ang defect.
Whether the defect is in the digital path or the amplification stage, a trip to the service center is inevitable.