Overridden custom functions have inputs locked when parent actor is altered

Overridden custom functions have inputs locked when parent actor is set to different blueprint type.

Regression (no) issue (does) occur in 4.12.5

1. Open Editor (any project)
2. Create new blueprint (actor)
3. Create child based on new blueprint
4. In parent blueprint, create custom function
5. Add 2 inputs (any) and 2 outputs (any)
6. Compile
7. Open child blueprint
8. In My Blueprint>Functions>Override>New Custom Function
9. Compile
10. Class Settings>Class Options>Parent Class>Set dropdown to "Actor"
11. Compile
12. Attempt to edit the inputs/outputs of overridden function