In most fictional universes (and Real Life), things tend to function in a particular, expected way, and perform that function consistently. Phasers have settings, guns will go off when the trigger is pulled (and sometimes when it isn't), healing potions will heal, and cars will ignite as they fly through the air. But sometimes the plot calls for an item to operate in ways that weren't previously established. This effect is unexpected, or even inconsistent with its previous known functions. But it'll get you through to the next plot point, and that's all that counts.