AFCAD file gives buggy ATC any idea plz?

Hi,Many people succeeded to make AFCAD files with multi ruwnays usage and when I looked at their AFCAD file I saw that the closed ruwnays are for landing and the opened one for take offs concidering they are the lonegst. Now here is my situation (I attached to this message a snap shot of my airport) I have 2 runways 03/21 and 17/35. I closed 03 and 17 to leave them for landing and left 21 and 35 opened for take offs as they do in real life, then I cheated by giving both same length so ATC will use them both (21 or 35)for take off depending on wind. However what happens in FS is very weird: ATC clears my aircraft very well to take off on 21 and to land on 17 when wind is in 17 range However and for some reason, ATC does not apply that celarance to the AI traffic! Instead it clears AI to take off on 21 and to land on 21. Very weird. Sometimes with the same wind it clears them to take off on 21 and land on 03 the opposite wish creates conflicts and endless delays for take off. I also saw once an a/c landing on 03 then exiting the rwy on the grass then making confused turns on th grass... I am very amazed as for why it is doing that to AI and not to my a/c. Any idea please?Thanks!Michel