What causes this - texture question?

[yellow5 0]

This happens every now and then at different airports, but not all airports. The grass will sometimes show through the runway textures. I would appreciate if anyone could explain this. I have included images below to show what is taking place. Thank you everyone for your answers....Kevin

[ahinterl 1]

My explanation is: when either the terrain where the airport is is not flattened and a different mesh is used or the AFCAD has changed and neither the flattening nor airport elevation in the AFCAD are correct, so the airport objects become partially overlapped by the surrounding area because of altitude differences.Solution would be to introduce a correct flattening polygon and/or readjust the airport elevation in the AFCAD file.But I'm no expert in scenery design, and I know of only one tool (never got it to work correctly for me) which could produce a polygon flattening BGL, so any other ideas here (it's something I'm suffering as well at different places)? Rectangulat flatten switches e.g. in scenery.cfg are always oriented in N-S direction, but how many runways are 18-36 or 9-27? So, would one really need a bunch of flatten switches with small rectangles to cover an e.g. a runway with 45 deg orientation?Andreas