That's due to the grid being stretched, the textures effectively are mapped to a square, distort the square and it distorts the texture, that's given me an idea that perhaps you could create a texture that looked correct when stretched, might look a bit odd when not stretched though?
The problem is less on a 5m grid, if the grid was say 1m which is not likely to happen, it probably wouldn't be that much of an issue.
The problem is less on a 5m grid, if the grid was say 1m which is not likely to happen, it probably wouldn't be that much of an issue.