Some of the intersecting numbers on the LfW board do not have a black square perfectly set at some of the crossings:
Between 46 & 47,
Between 30 & 50,
Between 53 & 68,
Between 139 and 164.
So... the dotted line 'seems to divert' just before hitting the square.
Can Jack can move past a policeman standing on one of these 'off-set' squares?