Missing Records from R/3 Production to BW 3.5 Production

Hi Experts

I am working on SAP BW 3.5 Version

When I am Loading data from R/3 Production to BW 3.5 Production half of the Sales Documents are Missing and I have done right LO-Cokpit procedure properly for

2LIS_11_VAITM

2LIS_11_VAHDR

2LIS_13_VDITM

2LIS_13_VDHDR

still problem

Kindly let me know on urgent basis( why it happens )

Thanks in Advance