I am running Sonar Platinum 2017.02 - and I have no idea yet how far back any Step Sequencer performance issues might go, but today, I was editing a project, in multiple Step Sequencer clips, and noticed some truly crazy bad jerky performance when dealing with multiple cells - such as trying to drag the mouse across multiple cells in the same row, or holding CTRL and dragging - to connect them.  
 
Either way, and the display and audio would suddenly get extremely jerky, and it would skip adding new cells in between others that should have produced a series of them when I dragged the mouse across empty cells to add notes in a row.
 
Further, it would lag way behind in producing audio for that row - and would both add cells and play audio for each added cell several seconds behind the mouse drags or clicks.
 
I had the same thing happen with a large ASIO Buffer Size, and also with it dropped down to my normal 128 Samples.  I also had these same issues with other projects that were far simpler - only 3-4 synths and no audio tracks.
 
I then went back to an existing project in X3, and there, Step Sequencer insertion of multiple cells in a given row, by dragging the mouse horizontally across empty cells in that row - worked as expected, smoothly and immediately inserting them.  Further, unlike in Platinum, only 1 single audio sound for 1 cell would play when I added 8-10 cells in a single mouse dragging insertion.  In Platinum, it was playing the audio sound for that row's midi note for each of the 8-10 cells I was inserting - which immediately got annoying.
 
I had not noticed the above behavior in Platinum, though have not done much with Step Sequencer of late there.
 
Has anyone else experienced the above kinds of performance, audio, and visual issues in Platinum?  
 
I will try rolling back several versions at a time, to see how far back these issues go, even if I have to go all the way back to the first Platinum version - I think I still have the download files.
 
Bob Bone
 

OK - an update to this issue:
 
I went through a series of rollbacks of Sonar Platinum, and couldn't determine any release where Step Sequencer performance matching my initial post began to occur.
 
Additionally, simpler projects throughout the range of versions I tested Step Sequencer behavior in had no issues whatsoever with the initially posted behavior.
 
Bypassing effects or adjusting ASIO Buffer Size had no effect on the performance issues.
 
This particular project does NOT exhibit any of this behavior when opened in X3, so SOMETHING is different between how X3 and Platinum deal with Step Sequencer, for a project such as this one.
 
This project has 49 total tracks, including maybe a dozen midi tracks, and the rest are either recorded audio or are audio tracks that are there for playback of midi track data.
 
Can ANYONE please check their Step Sequencer performance for some similarly constructed projects in Platinum - and then compare that back to in X3?  Thanks.
 
Bob Bone
 

Please can someone/anyone open up a mid-sized project that has both audio tracks and midi tracks, and just try adding some midi data to see if you too have problems with Step Sequencer getting bogged down for some reason when filling row steps/cells by dragging mouse horizontally on a given row to fill steps, then go back and do CTRL+drag to connect them into a single long sustained note?
 
As explained in my first two posts - Platinum is botching the above 2 tasks up pretty badly - whereas the exact same operations to the exact same project in X3 do NOT have those issues.  This project happens to have 50 tracks, of which about 15 are midi and the rest either recorded audio clips of guitar or they are audio tracks associated with midi output from soft synths (and therefore have no recorded audio clips).
 
I would REALLY appreciate someone helping me to confirm this is an issue that goes beyond my particular project/system.
 
THANKS!
 
Bob Bone
 

Just to say: This rings a bell. I just haven't had time to try repeat this but I will try in the coming week.

If you could test this out for me, you would be my HERO - I don't know when or why this behavior started, but I DO know that it has forced me to continue work on a current project - by doing all of my edits for Step Sequencer midi clips using X3, rather than Platinum.
 
It is driving me CRAZY!!!!!!!
 
Thank you SOOOOOOOO much for trying to help me with this issue.
 
Does ANYONE else also have the ability to check out these problems with Step Sequencer with some projects in Platinum?
 
Bob Bone
 

I've never used step sequencer. Wish I could help.