Download Android 7.1.2 stock firmware for Tanix TX9 Pro TV Box from here, here and here. Download previous firmware from here. Download Amlogic USB Burning Tool v2.0.8 from here or download Amlogic Burn_Card_Maker v2.0.2 from here.
Model: Tanix TX9 Pro 3GB / 32GB TV Box
Image file size: 683 MB
Platform: Amlogic S912
Built version: 2017 12 22
Kind of file: Full image (.img)
How to use: Flashing by Amlogic Burning Tool
System stability improved
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.