at what voltage does the fail safe decide that there is not enought voltage? The web site manual states that it operates from 3.8-6volts. Does that mean when your battery hits 3.8 volts it slams the brakes?
If your receiver battery becomes disconnected with a failsafe, pray you were hitting the brakes at the time. No, it will not help. This is where a throttle return spring comes in handy.