Sumvision Cyclone Voyager volume bug issue

[w13dle]

Hi all I have a Sumvision Cyclone Voyager 7" tablet for my son for Christmas, I thought id check it out make sure everythings ok put a few apps on etc, but I seem have ran into a couple of problems, the volume after a bit of use locks on full & when you try & turn it down on screen or by the buttons on side of the tab the icon goes up again its also done the opposite lock on low vol, if the tab is reset its fine again for a short while, it has also lost sound completly a couple of times but then fine again after a reset, I've updated to the latest firmware & the issues are still present, I'm quite familar with the jelly bean system I have a nexus 7/HTC One X+ , any help much appreciated