That might be a bad drain. Thaw her out. Clear the drain with hot water or blow it out best ya can and see if that fixes it. That is what you try first. If the problem still there ya might have a defrost problem. The defrost circuit consists of a heater a heater termination thermostat and a timer or defrost control. Every 8 hours or so the defrost control powers up the heater for 21 minutes or longer AND shuts down the compressor and fans.if the heater was to stay on for 21 minutes or longer it would melt the plastic ling and cook the frozen food because it is a calrod heater just like an oven element. The heater must shut down to prevent harm to the ice box so they install a small thermostat that shuts off power to the heater when the temp inside the evaporator sector is warm enuff ta melt frost. Most times the heater does not go bad if it is a metal calrod style, glass heaters do go out quite frequently however. The most likely candidate to fail in the defrost circuit is gonna be the termination thermostat. When that puppy fails the evaporator does not get the heat from heater and frost begins to build. It takes several weeks to get to the point that ice has dammed up into the evap fan and caused it to malfunction. The cheapest part is the defrost thermostat so if the heater is fine replace the stat and see if that fixes it. Other thangs to check for is loose or worn out door gasget and improper sealing doors. To make a door close tighter raise the support legs in front slightly to throw the doors tighter against the frame. That's all the smart pills I has for today. -PawPaw

If you need further help, reach me via phone at https://www.6ya.com/expert/dan_73bbd84fe1d95b61