Solution :
I think this is happening because of the name Conflict of Class (Model) names with the other reserved or the generated ones, but when auto creates the tables and Considering that EF Code First creates the intervene tables to relate the two or more of the tables using name of the tables for derived intervene table, so when you use the class name that employs a name like the intervene tables, we will get as such this ambiguous error.
e.g. If you have the Question class which has the navigation property with the name Answer then the internal model metadata will contain the reference called QUESTION_ANSWER
To resolve this, just try to change the class names which are used for generating tables and ensure that they are unique.