I don't understand what's wrong. I specified the coordinates relative to the mountpoint. But creatures are still passing through trees.

Moreover, 4 other cells became impassable instead of the four required ones.

By morning, the issue was partially resolved. I forced the computer to recognize the necessary cells as blocked, although by trial and error. The mountpoint was set at 30,41. The necessary cells had coordinates 36,38; 37,38; 36,37; 37,37. Logically, the blocked cells should have been (counting from the mountpoint): 6,3; 7,3; 6,4; 7,4. However, to achieve the result, I had to mark completely different cells as blocked: 8,8; 8,9; 9,8; 9,9. It is unclear why.