Excessive frost or ice buildup on the back wall or around the evaporator; airflow is restricted and cooling performance drops.

Safety warning: Unplug the unit before defrosting or removing panels. Do not use sharp tools to remove ice.

• Manual defrost: Remove all bottles, unplug the cooler, and leave the door open until all ice melts. Place towels to catch water.
• Clear drain: Locate the drain hole under the evaporator and clear any blockage with a soft brush or pipe cleaner. Flush with warm water.
• Inspect gasket: Replace a damaged "Door gasket" to reduce moisture entry.
• Check defrost components: If frost returns quickly, inspect the "Defrost temperature sensor" and "Defrost heater" (if present) as in the E4 scenario and replace faulty parts.