Indoor snow melt control failure, especially the SCP-120 and SCA-DUAL.
Observe control box. Is there a conduit entering the top of the box?
Open control box door and remove front panel. Inspect circuit board resting directly below the openings for the conduit or any other penetrations. Is there visible damage on the board? Are there visible signs of water ingress on the board or inside the box?
The circuit board inside of the box is not a user-serviceable part. The controller must be replaced if this board is damaged.
Condensation usually forms inside the sensor conduit if it is not sealed where the conduit enters the house's foundation.
To rectify this issue:
1. Replace SCP-120.
2. Seal the conduit with silicone or expanding foam where the sensor cable enters the conduit. This will keep the condensation from forming as air temperature changes for cold to warm or vice versa.
3. Install a drip loop in the conduit that can drain the condensation away from the controller and the PCB board inside.
See link for illustrated examples.