Here is a G-sensor (tilting) fix,
only tested it yet on a c91_1a model.
But it should work on all other c91 models.
Here you have a new
system.patch.zt280.tar.bz file.
You need to replace this with the excisting on the Zenibasic Rom, and install the Rom.
there is also another way, that worked for me.
so you don't need to install the rom again
But might now work for everbody, because there might be problems with ownership or permission, that will change.
you need root,and have a file browser with root acces and system file r/w acces
With es file explorer, you need to enable 'root explorer','up to root'and 'mount file system'
in the root setting in the setting menu.
Download the sensors.amlogic.so file.
sensors.amlogic.so
I also packed the file, somethimes this can make a different with ownership or permission
sensors.amlogic.rar
Copy this to you tablet,tf card or usb flash drive
Browse to the sensors.amlogic.so file on the tablet/tf-card/usb flash drive
and select copy, then you browse to /system/lib/hw
first rename the the excisting file from sensors.amlogic.so to sensors.amlogic.backup
So you have a backup file !
And then copy the file into the folder.
Reboot your tablet and G-sensor should work.
Browsing in Es file explorer:
usb flash drives -> Favorites, mnt/sda/1
tablet -> Favorites, mnt/flash/
tf card -> Favorites, phone icon, /sdcard
sensors.amlogic.so file -> Favorites, phone icon, /system/lib/hw