Changing tracks is slow


I have a problem with N6.5.30 (OSX Mavericks) which I haven’t encountered before. I just created a few PLAY instrument tracks for some percussion. They’re really short now, like a few bars, not much information since I’m just starting. By every time I change the track in timeline view, it takes a few seconds for it to activate. Whaat? Changing tracks to adjust volumes or anything else is now irritatingly slow and annoying.

Tried booting Nuendo and loading the project again, still slow. At the same time I noticed PLAY doesn’t still get the track volume, or is it because Nuendo doesn’t send it right to plug-in? This can be overcome by automation, but’s kind of slow extra step, if I have no other need for automation.

But this track changing slowness is annoying, any thoughts?