That's what I was saying when technology fails, you are in the deep do do.
If you totally reliant on technology you are asking for trouble.
Get cheap helicopter and learn to hover on one spot.
Yes, I understood what you were saying. Even a $30 or less copter to practice.
Since there is no way to switch out of GPS mode, once the H becomes a victim of GPS glitching, the pilot must helplessly watch his $1300 investment either recover or crash/fly away. The only other option is to cut the motors.