Hi, first off I have to ask, is this only happening to you on the rail network, and second, did you get the Alternate Rail Set before or after you got the diagonal fillers? It is in fact that mod causing this. I noticed where the missing fill is on your railway. Thats part of the rail tiles where there use to be corners, but the alternate rail set modded the textures on the diagonals, so in the end you now have no more corners, and with no more corners, you have nothing to fill anymore, because your corners have been eliminated from the rail network with that mod. I like having that mod, because I don't have to worry about those corners next to the tracks, but as for these diagonal fillers, weren't they designed more for road type networks? Maybe if you had a picture of these in action there?