Drum editor.

The Drum edit page is one of the main reasons I still use Cubase!
I’ve been using it for many years and, for me, it’s a great tool.

No idea what’s causing your machine gun fx- I’ve never had that problem.
It will sound notes if I drag them up or down (it’s playing the different notes) which is to be expected.

Nuendo allows the drum edit page to be used only via the NEK so maybe this is a factor.