Hi,
I think that it had to do with the range of the reset area. I have found that the defended area seems to have a larger reset range. As the bug happened when the POI was 57m (just across the street) the reset function crossed into the trader-protected area. Could it be that the flag that resets the quest area is not meant to cross into the trader area? Or it could be the above plus the other MODs I a running and they interacted in an odd way.