The 2 most common part(s) or condition(s) which cause the symptom Refrigerator defrost drain problems are listed below starting with the most likely. Check or test each item and watch any available videos.
If the refrigerator has defrost drain problems it's possible that the refrigerator has a clogged or freezing defrost drain. If the defrost drain freezes the defrost water will overflow the drain and drip down to the bottom of the compartment. Thaw any ice that is clogging the drain and make sure the drain is clear consider using an aftermarket drain heater to help prevent freezing of the drain in the future.
RepairClinic Item # 1914792
For refrigerator defrost drain problems check the drain heater to make sure it's working properly. If the drain heater is burned out or has come out of place the drain tube might freeze over.