No idea, but when its on 20 I lose the corner face and in your class you have
removeFace(this.faces[0]); removeFace(this.faces[1]); Would be my first "guess".
No idea, but when its on 20 I lose the corner face and in your class you have
removeFace(this.faces[0]); removeFace(this.faces[1]); Would be my first "guess".