Transposing Instrument shows preferred Sharps in the score, but renders as Flats when creating their parts

When working with Alto/Bari Sax parts where the instrument is set to "Prefer Sharps" and the song is in the Key of E their part transposes correctly to C# in the score (7 sharps), but the rendered part is in Db (5 flats). It seems I found out how to fix this in the past but cannot find it again. Any pointers are appreciated.