Cannot place banner

[matthew381]

we are trying to expand out village but that error is keep occuring. area is flattne, paved and inside of village. there is no reason to say that

1.png

simple map for better understanding

box with black line is original village area. we can build authority object in there so we managed to expand it a bit.

box with red line is expanded village area. its not even covering entire village because of error.

area between red line and black line is where the problem is. we try to place banner in that area but it wont work with "An authority object cannot be placed there" error.

as i said, area is flattened, paved and inside of village. I think there is no reason for error.
am I missing something? plz halp