An NPC from the tick area will not run the command/dialogue if the player is out of the NPC's field of view.

To cause a problem:
Create a NPC, create a tick area (/tickingarea) within the NPC, fly away from the NPC's visibility zone and write the command /dialogue

What should happen:
If the NPC is in the tick area (/tickingarea), the /dialogue command should be triggered, even if the player is out of the NPC's field of view.