Problem with a step from the SD 3 Master Class

HI - I have been learning to create a drum pattern / loop with SD3 by following the Master Class video (in Sonar 8.5). It's been going great and learning a lot ! However on the part about adding a third layer to a track that includes the ride cymbal and ride-bell pattern: the new pattern created "overlays" itself on the first layer - then on the tutorial he just drags that new pattern down to the third layer ----and the first layer pattern fills itself in at that gap. When I do that, the first layer / pattern leaves an open gap from where I dragged the new pattern !  Wondering what I am doing wrong to cause this.?