Whenever the sim casts a spell on himself or another sim...
On one lot from Moon Base Charlie II (a world), when my witch sim uses a charm on himself or another sim, they run outside to the fenced in garden area to do it. If the gate of fence is locked to keep the zombies out during a full moon, then they don't throw the charm because they can't get through the fence.
Does this have something to do with the gate of the fence being closer to the mail box than the front door? I tried moving the garden, but the gate is still closer than the front door. Humm. Okay, I'm gonna try that but I'll post this anyway just in case someone else has this strange behavior.