Inaccessible area for buildings

Platform: PC
Game mode: Private g-portal host
Version: 94750/17645
Problem: Bug

Inaccessible area for buildings.

It is impossible to place the buildings, the enclosures of a circle of sand columns, which I marked with a red line. Because of this, we do not get to finish the corner of the tower. There are no visible obstacles for construction in this area.