Hello, I can help you with this. You have a failed heater on your defrost system. Are you comfortable with hand tools and a voltage meter?
Yes I am, what next?
You will need to remove the back panel above the drawers and gain access to the three heaters. You can test each for continuity and determine which is failed. There is a large heater in the cooling tubes another under the trough that catches the water and a third in the drain tube that the water flows into. the other option is there is a kit containing the latter two heaters with an improved design available from Sub-Z. Let me know what you find. Thanks, Sam