Why do you keep on stating that an interfering signal only blocks a sensor for a fraction of a second. Interference is NOT limited to fractions of a second.at the same fraction of a second that an interfering signal blocks a sensor, a chance in some million?
( being accurate it blocks the receiver not the sensor ).
Why don't you look at the equipment that uses 433.92 MHz and see just how long some of it transmits for. You may find some of transmits fro several seconds at a time. Also extend your research into equipment that uses frequencies within the pass band of the receivers. ( as yet mdf has not provided any details of the pass band, you will need to find that information as well ). Then consider the harmonics of continuously operating transmitters, could these fall into the pass band with enough energy to block the receiver.....
To give you a clue as to why this is important
Broad band routers block receivers if they are too close to the panel or siren. Why do they block them ? Routers do not operate on 433.xx MHz so the receiver should not be affected by them yet it is affected to the point of being rendered in-operative.
It appears to be sub-harmonics and maybe side tones of the routers RF signal that falls into the pass band of the receivers and thus blocks them.