When the shells land directly on the roof it creates a earthen crater graffic above the Town Hall but does not register any damage to it.
Perhaps the area of effect is triggering above the Town Hall hit box?
Perhaps change the Shell AOE to a 3D radius to damage things bellow the impact point?
I have even been able to stand safely bellow a shell impact as described above to monitor that no damage was registered, though I did not have the forethought to grab a screen cap.
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