With the clicking etc it sounds like a mechanical failure?! A harddrive has several disks "platter"s stackt inside and multiple heads inside. They don’t necessarily all fail at the same time. Also sometimes there are just small areas affected that become inaccessible due to various reasons. They’ll probably grow at some point and you’re bound to loose more data. But if it’s an area of several consequtive blocks, it’ll show when you’re accessing those. And if your partitions and data are arranged serially, the next one might be physically stored where everything is still fine.