Thanks. Good fix was to avoid the green stripes . You basically corrected the y-coordinates to rewind the wide road blocks into the play area, so it should be the same for the smaller blocks of the event I called "NARROW" (the narrow road). I think, then, that it is simply a fact of y-coordinates which are not perfect although I have changed these y coordinates many times ! In the meantime, I copy the line you correct and paste it into my example, because I added a few things to it.