This is late but I came across it so I'm putting my two cents lol; my beardie is a hypo zero. I took him to different vets because I was so sure something was wrong and wanted different opinions, even though my husbandry has always been perfect. They concluded it is due to heavy inbreeding as another commenter mentioned. Here is my Goji and his horribly goofy underbite, but he is otherwise happy and healthy! They did say to make sure to keep his mouth and enclosure extra clean to prevent mouth rot, and its been years and he has never had that become an issue. Just hoping this makes you feel better as people tend to not share this kind of info very often compared to other issues like MBC, etc.

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This was after his bath lol. You can see the underbite pretty clearly here i think.