The description of the light sensor led me to believe the spell would be cast while the player is in low light. Not necessarily every tick just every once in a while. However the light sensor will only trigger when the player enters low light.

One example that comes to mind is :
The player has a spell that places a light block at their feet in their helmet. If a players enters a cave and the light sensor triggers while the player is in a non-solid block like Botania's Shimmering Mushrooms, the sensor will not trigger again until the player enter a bright area and re-enters a low light one.

I'm not sure if that behavior is intended or the description is suppose to be the right one.
Line 607 by the way.

Adjust your spell to use Trick: Break Block followed by Trick: Conjure Light

I changed my spell already. The issue, however, is that the descriptions for the sensor says "is in darkness" but the actual trigger is "enters darkness."