To downgrade or upgrade some special firmware for the FaceDeep 3 /FaceDeep 5 devices, you need to enforce the upgrade by USB Flash Drive. Otherwise may meet the situation of Upgrade /downgrade failure.
Here is the general steps:
Step 1: Please prepare the USB Flash Drive with FAT format and capacity less than 8GB.
Step 2: Copy the firmware file to USB Flash Drive and plug the USB Flash Drive to the USB port.
Step 3: Setup on device to enforcing firmware upgrade mode.
For detailed guidance, we take FaceDeep 3 for a reference