TMap entries are removed on Blueprint compile when using struct as key

Map entries are removed on Blueprint compile when using struct as key. 

1. In the editor, create an enum type and add some values. (TestEnum -> "EnumA, EnumB, EnumC")
2. Create a structure type, with a field for this enum and a bool (TestStruct -> [TestEnum, bool])
3. Create a BP object child of UObject. Add a variable TestVar, mapping TestStruct to integers.
4. Set two elements on the map, (EnumB, true) -> 1, (EnumB, false) -> 2
5. Compile the BP, and notice that the second element gets removed, even though you'd expect the structs to be two different valid keys.