[Solved] MIDI playback bug ?? Sonar Platinum 2016.05

hey Guys,
 
I have a song that has a monophonic bass part played by Minimonsta
for some reason, not all notes play when I play back the project - this has not always been the case. for quite some time, it was playing back fine but something has changed & now not all notes play. It's not a polyphony issue with the plug in as I have it set to 8 notes, and its a monophonic part
Strangely, if I freeze the track, everything renders and then plays back properly ( all notes in the sequence) 
to see what I mean, I did a quick Video 
 
makes me nervous about other tracks an missing notes - this one was really obvious but i may miss more subtle parts if they aren't playing correctly. 
 
Chuck
 
 Sonar Platinum 22.5.0. build 43 X64 [2016.05]

also sounds like a buffers issue to me as well.
This :  "if I freeze the track, everything renders and then plays back properly"
sounds like a tell tale sign.

500 was the pre-X1 default, and as far as I can tell it is close to 'ideal' in terms of being effective in preventing dropped notes while not introducing any undesirable side-effects. I have had issues when experimenting with very high values like 2000, but don't recall the exact symptoms. Personally I've never encountered a project that needed more than 550ms to fly right. But it depends on the project and the specific system.
 
Below is a post from Noel Borthwick on the subject. At the time he mentioned that the next update (X2A) would have an auto-sizing function for the MIDI buffer, but the OP later reported no joy with it, and I did not see any evidence that it was working, either; 250 still caused problems for me, and I've been at 500 ever since, only increasing it when I have PDC-inducing plugins in the project as Noel's post mentions (though I usually try to have MIDI-driven tracks frozen at that point):
 
http://forum.cakewalk.com/FindPost/2730354
 
I believe this is a 'legacy' function to some extent, coming from a time when the average PC had a hard time keeping up with the demands of real-time soft-synth rendering, and it might now be causing more problems than it solves in a lot of cases. My evidence for this is that if you take a project that's dropping notes at a given buffer size, and route all the MIDI out to physical or virtual MIDI ports and back into SONAR as 'external' MIDI inputs, it will play fine with the soft synths rendering the live MIDI input in real time.