Self Shutdown problem with Onda V989

I purchased Onda V989 AIR Octa Core Tablet PC 9.7" IPS Allwinner A83T Octa Core 2GB+32GB Android 4.4 on 3 December, 2015. I received it in January, 2016. After just one-month's use it has started giving me problems.
While browsing or playing basic games ( Candy Crush etc ), it just shuts-down by itself. Battery level is always adequate, and its not on low battery.
This self shut-down issue has increased so much, that I am thinking of just throwing away this tablet in trash.
I contacted the seller on AliExpress, but they have not been very helpful to solve my problem.
Does anyone here has any idea , what can be the issue ? and how to solve the same ?
Thanks in advance.
Omar Chaudhry
omar@digimart.com.pk