Hello, the problem is probably caused by liquid entering the tablet. iFixit has some excellent guides and wikis for this specific issue that should provide a good starting point for your repair. I’ll share the links below, but here’s a quick rundown: you’ll need to open the device and clean off any corrosion from the internal boards. Depending on the extent of the liquid damage, you might also need to [guide|6519|replace the battery].
I know that this answer is a few years late, but hopefully it will help anyone else experiencing a similar issue.
* [[Electronics Water Damage|Electronics Water Damage Wiki]]
* [[Laptop is Liquid Damaged|Laptop is Liquid Damaged Wiki]]
* [guide|95280|iPhone Liquid Damaged Repair Guide]