Unusual accidental activity - (courtesy accidentals?)

I have a score in F minor, so 4 flats.

There is a Gb/A chord, and the display of that chord seems to break normal accidental rules if I use a key signature.

If I do not use a key signature the flats for both Bb and Db are both displayed (correctly). However, if I use a key signature of 4 flats, the flat for Db does not display (correct) but the flat for the Bb DOES display in front of the note (incorrect) even though it is in the key signature.

I have saved a simplified version of the file both with a key signature and without for your review. Am I doing something wrong? or is there a bug? Is there a workaround?

Thanks in advance!