Lighting Contactors can cause relays to latch to the wrong state
There were isolated incidents in the past that lighting contactors were observed to have been causing problems to the relays. The relays were randomly latching to the open state even after being turned on.
This is NOT a product nor design issue. The reason is due the inductive noise coming from the contactor that is being kicked back to the relay drive circuit. These devices are considered to be inductive loads which are not the typical load a lighting control panel controls.
There are a lot of factors to consider, such as manufacturer, load type, amperage, voltage, distance from the contactor to the relay, etc. But the quickest solution/fix is to add a snubber (RC Filter) device across the line and load terminals of the relay. The snubber device will filter out the noise that affects the relay drive circuit.
NOTE: Depending on the voltage that drives the lighting contactor (120V or 277V), the correct snubber specification must be used.