The Evil in Green

The crude detector seemed to win the favor of the green-clad weirdos. Soon, they issued a second commission, requesting an escort for a new location to continue searching for ruins.
However, a problem quickly arose. The issue wasn't whether the detector could find ruins, but that the device itself exhibited an inexplicable anomaly. Four people would hear a sound at the same time, but describe four completely different results. Some heard one knock, some two, some four...

When cracks appear in reality, people always try to patch them with what they know. The green-clad weirdos were no exception. Their explanation was that some evil spirit had targeted them in this place.
However, even after changing locations, the phenomenon persisted. The four of them still simultaneously heard four different patterns of knocks. The atmosphere grew somewhat eerie...

In the end, the detector itself bailed them out: a wisp of fine ash-like mist escaped from its seal as it sat on the ground. This unrolled in the air, weaving into strange shapes, and finally settled neatly into a vortex-like triangle. The next moment, it was blown away by a gust of wind...
Terrified, the green-clad weirdos fled, and the matter was left unsettled.

Caught between laughter and fear, no one bothered to ask what caused such discrepancy.
Was the detection method unreliable? Was there truly an evil spirit? Or had that familiar vortex-like triangle appeared once again?
For now, the answer remains unknown. After all, not everything can be explained. Or perhaps there's more than one answer...