I have just purchased a 7" android tablet from ebay. Model number is WM8850-mid. The first problem is that it wont charge and only works while plugged into the power adaptor. The second problem is the touch screen behaves oddly, even operating by its self. It works normally if I connect it to my PC via the USB cable. So basically, the only way for it to work is to be connected to power and usb. Thanks in advance.