Im making a crocodile player type, (Well I can't make player types, I do it just for fun) but there seems to be a problem when Im rotating the crocodiles mouth. The groups connected each other. I didnt regroup them or something like that.
On the first picture, I hided the upper mouth group. Everything was normal, no faces dissapeared.

But when I try to move the group, some of the vertices stay on their first point.

I don't know what to do so halp mah plz.