Sorry for not posting the save, when noticed the behavior I played on without saving and remembered just later to write it down
Now I'm attaching saves from three scenarios I set up to testthe behavior - happens to me in all three (in one the arty is naval, in other it is on-map, inf. howitzers, last is medium arty) - in any of these the Sherman AOP bombards the arty target hex instead the "Z" fire target (in all three located 3-4 hexes in front of the tank). Noticed now the target hex changes right after arty plotting.