There were two issues discovered: - Triangles mapping didn't free in buildNavMeshData if there's no recast data for an object - KX_NavMeshObject used not-guarded allocation for polygons storage, but used guarded freeing stuff to free used memory, producing error messages in the console and leading to memory leak. Wasn't actually harmful for users -- there was no memory corruptions and error happens only when object was set up in a way when navmesh can't work in theory.