Why does my game crashes at the end of a destructor?

Made a Json wrapper over the ue4 Json logic. It behaves like a JavaScript object but with methods.
Used it as a property of a thing called BuildingBlueprint.

Using BuildingBlueprint as input pin in a function node, for some reason, makes the destructor of JsonWrapper throw an error and trigger a break there.

I am new to visual studio, coming from an Eclipse background and frankly I am lost, how to debug this?

Debugging with Visual Studio works great.