Light artifact issue

[Hjorimir]

I'm not exactly sure what to call this, but I'll do my best to describe it (I've included pictures).

I have two characters on the map here. One has a light (effect coded as "Torch; LIGHT: 10/25 ffffd500 flicker"). The other is surrounded in darkness (effect coded as: "Darkness; LIGHT: 15/15 ff000000"). The darkness effect does a great job of shutting down the light and visibility of torch character (and it shuts down darkvision as well, which is perfect). However, when/if the torch character enters and then exits the area of darkness, if I then move the character with the darkness effect, a light (exactly like that of the torchbearer) has been left behind on the map. Images attached.