Using Transpose Tool on Score does not change Part key signatures

When using the Transpose Tool on a Score, the key signature of the score will change correct but the parts' key signatures do not change. The notes of the parts are transposed but the key signature remains in the original signature. The only solution is to manually select and change the key signature for each part.

To recreate:
1. Create a score
2. Create the parts for the score
3. Select All in the score
4. Use the Transpose tool to change the key signature for all parts
5. Make sure the "Transpose key signatures" is ticked/checked
6. Score will have notes and key signatures in all parts transposed
7. Parts only have the notes transposed