I have a gas 2 zone boiler and when A zone's thermostat turned on, everything runs smoothly but when B zone's thermostat turned on, sometimes, caused the small relay boxes on the relay board to make a fast clicking sound, which turns the boiler on and off. What's the problem? Do I have a bad relay board? Wrong wiring between the thermostat and the relay board? How can I solve this issue? Are there other causes to the issue? Thanks!