Lenovo LOQ only charges when closed - refusing repair within warrenty

I bought a Lenovo LOQ back in November, and a few months ago it started only charging when completely closed over. It's been used pretty lightly since I bought it.

It was within warranty so I raised a repair ticket and sent it off, and they've come back saying it is customer induced damage and therefore not under warranty, and wanting to charge more than the cost of the laptop to repair it.

I'm not a hugely techy person, but my understanding is there are known faults with the motherboards in the LOQs and that's likely what's causing this issue - is that right? Are there any resources I can point to so that they will repair this under warrenty?

It's also my understanding that in less than a year of light use and always using wall sockets and the charger that came with the laptop that it's extremely unlikely I've done anything as the user to cause this issue, but is that right? Is there anything I might have done to cause this issue?