I think it’s bug. A new project. A couple of track. Use the same vsti instrument on each track. Play different notes. In track scopes show waveform ONLY last note_on-ed track (in mixer view too), but playing right. With sampled instruments all fine. The attached project is example. It’s happens with any vsti, for example i use free augur vsti (get it from here http://www.vstcafe.com/2009/05/smart-electronix-augur.html)
It’s not a bug. It is how Renoise handles VSTis 
It happens with VSTI’s that do not have multiple output channels, or you didn’t attached them properly to their respective tracks.
See plugin routing on the documentation for more info.
Sorry guys. Thanks a lot. I just forgot about Output panel settings