Hasta La Motion!

This is something strange i just found out on the mesh that iam trying to build. Pictures describe it better:

first picture: this is one apparently simple vertex linking 3 edges.

second picture: just as i moved it, it appears it wasnt alone

third picture: a whole lot of hidden faces were here. The starting vertex was in fact three vertices in same place.

Worst still, about ALL vertices on this mesh has this problem!!

I really dunno how it happened this way. All i did was to start with a cube primitive, add 1 subdivision, deleted left side faces (i’ll mirror everything later on) and extrude faces.

How can i fix this issue? What is the name of this kind of issue to begin with?

Attached Thumbnails