Incorrect display of custom key signatures

In a blank piano score, open the master palette and under "Key Signatures", create a custom key signature (e.g. A♭) and click "add".
Add this custom key signature to the score. Notice that the bass clef staff incorrectly displays the key signature at the same position on the staff as the treble clef staff and thus wrongly displays a C♭. This means that a custom key signature will only display correctly if the staff has a treble clef.
See attached score for an example of this issue.