Huh, odd. It seems like the Static Mesh of Tile_Hex_Empty was set to 0.5 unreal units above its CustomGridAnchor, meaning it occludes the marker meshes. Set it to 0 and it should be fine. I’ve now fixed it for the in-progress version for the next update. Thanks!
I’ve now come far enough with the update, that I’m pretty confident I will be able to release it around the same time as UE4.15 is out, by the way.