Old and Bold RC PILOT
You experiences with older equipment were typical of the time and the technology.My experiences going back to motor rudder combos in early escapement systems ( late 60's) show that the electronics will do just about anything they want when you turn them on. That was why you started the radio system BEFORE anything else or why you null memory on startup.
Thanks for the update @Hai-Lee , been wondering how it was going.
Modern digital radios use microprocessors in the transmitter, receiver and even in the ESCs. Each of these processors has a boot up sequence.
As part of each units boot up sequence there are safety features to ensure that the unstable and unsafe initialisation of the past are gone.
With modern digital radio receivers and ESCs each will not enable the motor circuitry or will not supply a throttle channel output until after the boot up sequence is completed. The only way to complete the boot up is to have the bound transmitter signal present and being received.
We all should know the FCC required Failsafe but most do not know of the FCC required collision avoidance feature of the transmitters. If the transmitter jumps to the next channel in sequence and the channel is busy the transmitter will not transmit over the other signal. The transmitter now is to only way to actually enable the motor drive circuitry, (excluding something like a servo tester of course).
It is quite possible that you have unknowingly already had the model boot up without a valid transmit signal due to spectral congestion and you just did not notice or the model just took a bit longer to initialise.
Computer control is here and getting smarter and even safer.
I just prefer to handle my models when I know the motor cannot activate ever!!