Overridden Interface Functions in Child BPs lose array output pins after closing/reopening the project and become invalid

Overridden Interface Functions in Child BPs lose array output pins after closing/reopening the project and become invalid.

Reproduced in Main //depot/UE4/Promotable-CL-2434822

1. Open any project
2. Create a new Interface
3. Give the Interface's function an Output of any type
4. Make the output an array
5. Create a new Actor Blueprint
6. Implement the interface
7. Open the function in the Blueprint
8. Make Array > attach to the function output
9. Create a Child of the Blueprint
10. Override the function from the Parent BP
11. Make Array > attach to the function output
12. Save All > Close Editor
13. Reopen project
14. Open the Child BP

Results:
Compile error. The function's ReturnNode no longer has an output pin, and the log says "The function name [FunctionName] is already used"

[Bug] UE4 Editor (origin/master) with Blueprints and Interface-BP: Forgetting return values