I have an annoying issue which should be simple to solve but never been able to find out how!

I use a Logitech Harmony One to control my Samsung TV and VU+ Duo and sometimes when i'm playing a file and press "6" to skip forward it somehow activates the mute on the Vu+ meaning i then have to use my remote to select device>vu+ hit mute (to unmute it!) then press activities on the remote to go back to watching the file...

If I could disable the mute on the VU+ my problem would be solved!

any ideas?