And moving it left or right doesn’t matter – it never ends up centered properly. Appears not to be a problem when applied to the top of the car, however.
This I think has been a persistent problem with the paint editor. I usually just use a single thin stripe on the car and center it. I then base my alignment off of the stripe and not the (x, y) values.
[edit] I base my center off of the stripes (x, y) values instead of the editors (x, y).