They're not missing, it appears to be a wrong MCD record value for the 'bigwall' field that's making that wall 'walkable'. Comparing it to the same MCD file in TFTD shows that it was originally 1, so it has been changed at some point. The current value of 9 matches the pathing the units are taking in those screens, 9 blocks the north and west side of the tile, but leaves the east and south sides open to walk, and a value of 1 fully blocks the tile.
Edit: this would affect other mapBlocks too if they use that record, at least fixing it there will fix all of them.