I have the same problem, there seems to be a manufacturing defect in some of the products, I approached the service center about this, while it was under warranty. The guy over there said that mine was the third such case at their center, but the lenovo senior officials refused to replace it under warranty (and also the other two unlucky customers, who chose to buy lenovo over others, like me).
I also wrote to them explaining that it was a manufacturing defect, but still they maintained that it was physical damage, and was not covered under warranty.
What seems to be happening in my S10 is that, instead of the hinge taking the full load while the lid is being opened, the part just above the hinge takes the load and bends to some extent while opening the lid. Over time, this has caused the plastic to crack.
The lenovo service center said that they could not get the lid, or even the whole body shell for me, even if I paid for it.
So now I'm using it with a cracked lid (near the hinge) and already some small pieces of the lid have fallen off, and the cracks are moving upwards.
I guess it's just a matter of time before I have to throw away the whole laptop, because, if I'm right, the display interface, webcam and wifi connections also pass through the hinge, and if any of those break, it's as good as junk.
And this has not been the only problem, I had the motherboard replaced once under warranty, since the keys below the touchpad stopped working. And more recently, just after the warranty got over, the charger stopped working, since the wire near the charger pin that goes into the laptop frayed and broke from the inside. I repaired the charger with a little DIY, by cutting open the sheath and connecting the broken wire back again, and covering it with insulation tape.
Though a crude solution, at least it works now, since I would definitely not have spent any money to buy a charger for this poorly built laptop.
All this in just one and a half years of very light use, and absolutely zero physical abuse, including 99% usage indoors. I have carried it along only for maybe 4-5 days, in my bag.
Having had my share of laptops, this was, by far, the worse build quality I have ever seen in my life. Well, I still have a Pentium 2 Dell latitude that still works just fine, after so many years of use. That is what build quality is about.
After this bad experience, I have completely lost faith in Lenovo products and will never buy a Lenovo product ever again, and would advise others to stay away from lenovo too.