Make Bitmask node returns incorrect value when using custom Enum

When a custom enum is used as the Bitmask Enum of a Make Bitmask node, the value returned does not match the expected value

1. Open UE4 Editor
2. Add Code to project based on Actor (MyActor)
3. Add the following code to MyActor
   • .h

     UENUM(BlueprintType, meta = (Bitflags))
     enum ETest
     {
     	BITFLAG1 = 1 UMETA (DisplayName = "BitFlag 1"),
     	BITFLAG2 = 2 UMETA(DisplayName = "BitFlag 2"),
     	BITFLAG3 = 3 UMETA(DisplayName = "BitFlag 3"),
     	BITFLAG4 = 4 UMETA(DisplayName = "BitFlag 3"),
     };
     

   • .cpp (in Constructor)

     	TestBitmask = 0;
     	TestBitmask |= ETest::BITFLAG1;
     	TestBitmask |= ETest::BITFLAG3;
     

4. Compile
5. In editor, create blueprint based on MyActor
6. Add Get TestBitmask node
   • From return pin, create ToString(int) node
7. From BeginPlay execution pin, add Print String node
8. Wire ToString node to Print String node
9. Create duplicate of ToString and Print String nodes
10. Right click and create Make Bitmask node
11. With Bitmask node selected, set Bitmask Enum to ETest
12. Check BitFlag1 and BitFlag3
13. Wire Make Bitmask node to duplicated ToString node
14. Wire Print String execution to the duplicated Print String
15. Add instance of MyActorBP to the level and PIE

Result:
First Print String (from code) prints 5 as expected. Second Print String (Make Bitmask node) prints 18.

Expected:
Number 5 gets printed to the screen twice.