Contact their customer service. I had a similar issue and they replied. See if your device has some sort of faulty hardware which in this case you can return to them.
I had a similar issue but with my A5 2016. I think it's due to gaming for prolonged amounts of time on CPU and battery heavy games. I think this doesn't provide enough time for it to ventilate especially that it's a SmartPhone. I used to place it in ...