Hubsan H501S firmware downgrade
I just try downgrade the firmware from 1.2.2 to 1.1.8 and it is easy as it is upgrading. No issue with GPS mode or unlock motors, if you have upgraded to 1.2.3, 1.2.5 or 1.2.6, it cannot be downgraded.
Firmware 1.1.8
https://www.sendspace.com/file/fok62g