To fix it you have to allow "natural" move ins until Muffy appears. She is in your void queue.
By natural, I mean that you have an empty plot and wait until a villager moves in that you did not invite from an insland, campsite, or amiibo. IT can take a few villagers, but Muffy is in there and will eventually appear.
It is caused when a villager from someone else's town is trying to move in and you scan that villagers amiibo. If you are only cycling popular amiibo, you are less likely to encounter this issue as people are less likely to just void those villagers.
By natural, I mean that you have an empty plot and wait until a villager moves in that you did not invite from an insland, campsite, or amiibo. IT can take a few villagers, but Muffy is in there and will eventually appear.
I have been cycling amiibos and I haven't experience this, it was Colton, Marshal, Colton, Marshal, Flora, Marshal and finally Flora. The only voided one was Colton.
It is caused when a villager from someone else's town is trying to move in and you scan that villagers amiibo. If you are only cycling popular amiibo, you are less likely to encounter this issue as people are less likely to just void those villagers.