Cubasis midi track mixdown and saving midi file

Using cubasis with audiobus and Gestrument or Musix pro for data imput, once the midi track is recorded i made a mixdown but the resulting mixed down midi track comes out wrong. Let me explain it:
Less say i record a 4 bar midi piano and mix it down cheking out the 4 bar locator. The 4 bar midi trak becomes a 400 bar monster midi track once is mixed down into the media bay.!
Is there something i am doing wrong?
It must be some kindof bug, have you had similar prolem from other customers? I wonder