The gender is only automatically updated when a profile is first created. If an error is made due to a unisex name (or any other reason) when the prefix is corrected the gender must be manually updated. Same thing with salutations.  If it is going to auto populate based on a selection then when that selection changes it should auto update, or have some sort of pop up message to draw attention to the gender and salutation fields. We have had mis-matched data because initially it wasn't realized that it only auto populated for new records.