As compass is quite sensitive and may be interferenced with on small copter, especially FPV drones.
As I have met this issue here: Why magfit's output result is out of parameter range?
And I know bf/inav has got GPS(no compass) working for RTL. Ardupilot has Dead Reckoning Failsafe — Copter documentation and RTL/Smart RTL.
So is there any possibility to intergrate all those methods for graceful degraded RTL.
SmartRTL > RTL > RTL (with compass) > Dead Reconing, bit mask for enable or disable???