Excessive frost buildup in a freezer can be caused by a few potential issues. These include:
The defrost timer may be malfunctioning, preventing the appliance from regularly de-frosting itself.
There is a leak in the door seal, allowing warm air to enter and leading to excessive condensation.
The thermostat has been set too low, causing the interior temperature to drop too far and creating excess frost.
The evaporator fan motor has broken down or become clogged with dirt, preventing air circulation and leading to frost accumulation.