[77newell]

If the power supply to the red relay also powers the light then there is resistance in the supply circuit before it splits to supply the two devices. I'm thinking that the coil in the red relay holds ok until some new load is added to the circuit which drops the voltage. When the coil drops out, the total load decreases so the voltage rises to the point the coil pulls in again. Something like this is happening because every time you do something that reduces electric consumption the red relay stops clicking.