I have a MusicXML file for a project in B Major. Upon importing, it displays the proper key signature, but all parts except piano show all the accidentals on the notes, too. I had similar experience in another software title, too, so I’m guessing it’s something in the XML. Is there a way to remove the redundant accidentals? I like courtesy accidentals when appropriate, but this is ridiculous! 
It was easy enough to correct this by selecting the notes (the whole LOT of them, had to do it singly and in small groups) and clicking the sharp selection tool. This removed the graphic without changing the pitch, thank heavens.
You can also use Edit > Reset Appearance to remove redundant accidentals, though you do still have the problem of selecting all the notes in the first place.