As you can see, the area "skips" the skeletal enforcer at the bottom, and this cell impact is displaced on the wizard instead. If I move the point of impact one cell further, the skeletal enforcer stands just outside of the range and this skip effect disappears.
You can also see that this same enemy was not at all impacted by the fiery presence spell cast by the paladin, it did not take a dice roll, only Mardracht and the wights did. It seems for some reason he's considered as a friend (that's in the known issues). Not sure if that's related, the party members don't have this skip effect on the fireball. It rather looks like a 2nd bug on the skeleton enforcer.