Mine also began booting into BIOS and rebooting into dead screen bios. I left it alone for a few days. Came back and the screen was stuck in fastboot DMX mode. Restarted it and everything was fine. If you hold down the power and vol down buttons after it’s been powered off then as soon as you see the teclast Chinese writing let go and you get into fastboot DMX mode. Then power down again and power up you should be fine.
I tell ya something is wrong with these tablets. I was tempted to buy the X2 pro but after my experiences with this X98 Pro no way. No more tablets from aliexpress.