Moving items/objects in Cubase (drag & drop) sometimes fails

Hi! I have a problem with Cubase.
When I have many items that I want to move by drag & drop sometimes some of the items I’ve marked and dragged do not simply move. Say I have selected 300 items and I drag them 4 bars. Then perhaps 7-8 of the items will stay in position and 6-7 items will be placed randomly somewhere between the start position and the position I dragged them to. The other ~285 items will be perfectly placed.

Is there any way to get around this problem? I use Cubase 5.