I just joined today as I am having exactly the same problems.
About a week ago, I noticed that several recordings I'd made were dropping sound and video every 15 seconds or so. But when I rewound, the dropouts weren't there. Went to Argos to see what I should do, as they're not in stock anywhere now, and was advised to bring it back for a full refund.
Before I started packing it up, I found this forum with other people having the same problems, so I'm going to hold onto it for a while longer in the hope there's a fix. Although there have also been instances when it just turns itself off when I'm in the middle of watching something
Anyway, glad I'm not alone.