This bug is caused by Google app, because Ok Google feature is enabled.
To fix this, you need to reboot your tablet to Safe Mode.
After reboot, don’t unlock the tablet, must stay on Lock screen, hold Power button to show power options, hold Restart option and A window will appear indicating that if you want to reboot to safe mode, click Yes (if you can’t click Yes because the window is bugged, try use screen in vertical or use a USB keyboard to select Yes).
After the tablet reboots to safe mode, go to Google app settings, disable Ok Google or just wipe Google app data to restore app settings to default.
Then reboot tablet and the problem will be fixed.
It’s probably that Google already fixed that and you must update Google app in Play Store now, since 2 days ago, I just enabled it again and it was fixed.