OK. So I figured out the problem.
I had created Identifiers for ALL of my entity's properties instead of just creating identifiers for only the properties that makes the specific entity unique! I had created identifiers for properties that had null values and others that were of type DateTime that do not at all uniquely identify the entity. As a result, when trying to perform a refresh on the external list data, it was trying to retrieve the external data for each of the individual list items with the assumption that every single column/field in the external list was part of the unique identifier for a particular list item. Obviously that prevented the data from refreshing correctly.