Copying and dragging notes in staff view

Hi,
 
I experienced a weird bug: When marking notes in staff-view and trying to copy them (by Drag'n Drop + STRG) the marked notes will be copied, but others suddenly disappear. Also moving notes will lead to further notes to disappear. Is this a known bug? Is there any solution? I can add a video showing this behaviour. Would be great to get a solution soon!
 
Thanks and best,
Chris
 
P.S. Sonar X3d Producer on Win7