I am not a tech....but have fixed a similar problem thanks to help from the forum. The "duck bill" issue affects many models and brands, especially bottom freezer. First problem is that the rubber duckbill funnel is not even shown or called out on the parts diagrams!
First, your symptoms would just be water leaking from lower edge or corner of drawer, and thick ice buildup on bottom of freezer liner. OPERATION AND TEMPS of the refrigerator and freezer are normal.
If your unit has this, it is attached to a tube which directs defrost 'melt' water from freezer to the "down under" area. Because of localized heat, the rubber gums up and blocks the drain. In my case ( Maytag) it is accessible by removing a small grill panel on the OUTSIDE rear of the unit, right down near the floor. Easy access....did not have to take apart the INTERIOR evaporator covers.
Again in my case, Maytag had issued a tech sheet on it, which AJ was kind enough to send to me. Probem solved!!!!
So, if your symptoms are as I described, follow up with some clarifying info for the techs on the forum and go from there.