I set the gender for the Moki in one save, and when I started another, it defaulted to the same gender I chose in the first save without giving me the option to choose again in my second save. (Probably not a huge loss, especially if you can customize them like the other lovers, but I was curious to see what the default gender was.)
Edit: They showed up and used the wrong pronouns (I guess that their default gender is female), but since they can be customized, there's no harm done. Just a quirk.
Edit: Another bug during Ori's event with the Moki was that an event started (Flo and Sean swimming at the lake, commenting on his old backpack) and after that Ori started showing up in the forest despite the fact they aren't supposed to be there during the Moki event. (Probably because meeting Ori during the backpack event is scripted.)