Something is going wrong with the ground texture. This is the view from Blender and NWN-Explorer:
I got the same from the compiled and uncompiled version. The problem appears on more than one tile.
But ingame and in the toolset, everything seems to be correct. This is how the floor should look like:
Hmmm, now Iām a bit mixed up
(Tileset: Granite crypt, Tile tgc01_a01_02)