Is the main key on a ring with other keys or odds and bobs and the spare on its own?
I've had occasional trouble with my m/home as my StrikeBack immobiliser activates, preventing me from starting the engine even with the correct key or the spare in the ignition.
An AA chap said it's quite well known to happen if it receives stray (blocking) radio or microwave signals. E.G. a car park (hospital) CCTV, Security staff radios, Phone mast or vehicle and traffic monitoring systems.
The last time I had it happen the AA chap and I pushed the m/h 10 yds and all was good again.
Apparently the environment is absolutely saturated with radio waves of one sort or another.