Solenoids, large relays, and motors can create a lot of electrical interference. This can wreak havoc to nearby electronic devices. If you notice the sound from a controller is stopping unexpectedly when controlling one of these devices, this is most likely your problem. The solution depends on whether you are using AC or DC “loads”. For AC loads a capacitor is used and for DC loads a diode. The best place to install is as close as possible to the load, if that's not possible then across the terminal block on the controller is second best.