It's not a bug, AI is not coded to walk above a certain height above the terrain, hopefully after the EBE is released and Lee starts work on the AI update we will be able to place them wherever we like.
i5, NV960 2GB, 16GB memory, 2x 2TB Hybrid, Win10.
i3 , Intel integrated graphics, 6GB memory, 512GB Generic SATAIII Win8.1.
Intel Celeron (duel Core), Radeon integrated graphics, 4GB memory, 180gB Generic SATAII, WinVista.
Q6600, Intel integrated graphics, 8GB memory, 512GB Generic SATAII, Win7.