Guitarpima
It's not the 0. I hit it and the line appeared. I hit it again and it went away.
If it's a vertical line that is appearing and disappearing when pressing 0 on the numeric keypad that is "Enhanced mode" which causes all sorts of odd happenings. Very easy to get into without realising as well.
I believe it is something to do with the VS-700 but not entirely sure as I don't have one of those.