MetricBoilerPlate must be a Navigator to another entity.
Could you please check the Designer and see which Navigators you used to have in v.1.x and compare them with Navigators found in the 5.7 Designer?
It might be a m:n Navigator which is not generated by default anymore, as there is a setting for many to many relations in Database First Development section in the Project Settings which is false by default.
Please let us know your findings.