Sound on dvd recordings

I have the Toshiba DVR D-R410KU and have had no problems with it until I started recording a tv show and even though I am watching it with the sound on, it records with some sound and some times it is mute.

Any suggestions? Thanks in advance!

Perhaps it’s a setting for SAP (second Audio Program)? Our local CBS has SAP and half the time there’s nothing on it.