After I use Windows, I have to shutdown and reboot pushing and holding the power and up-volume buttons until I see screen activity. Otherwise I would not get the option to choose which OS to startup. Rather the device will boot straight into Windows. Good luck.
I have Teclast x98 and I downgraded it from window 10 to window 8.1 due to different issues that am tired of but I discovered the dual boot is not working . The android disappeared, its only the window I have on it and option of dual boot usually bring only window. Please help me.