In my latest project I have recorded a MIDI bass track. During playback the track randomly drops notes or a note may sustain indefinitely (not seeing a note off event?). It is NOT caused by any erroneous CC data as the location of the problem varies each time I play it back. If I start the song at measure 1 and get a dropped note (or sustained note) at measure 10, I then place the now time at measure 7 play from there and there is no problem. The next time I play back the problem might be at measure 20, the next time at measure 15 or measure 48. It appears totally random. I have been using Sonar for 9 years and this is the first time this has ever occurred.
Any thoughts?
 
I am on  Plat 201611. The track is triggering an ext synth. I'll test tonight whether or not it happens with a VSTi.

In Preferences, experiment with the MIDI buffer size. Based on forum posts where MIDI issues are solved, this seems to be the most common cause of MIDI strangeness. The setting does not affect audio latency.

A possibility might be the sustain pedal CCs, if you are using any sustain.   Sonar treats pedal CCs very very oddly for CC64 values that are not 0 or 127.    So if, possibly, you have used the PRV controller pane to 'draw' sustains at some point, this could be your problem.   A value of 1 might look like 0 visually, but it acts very differently. 

Thanks for the replies.
Craig, buffers are at 128. Doesn't seem to matter.
Bill, there is no sustain pedal used. Played a bass part on my Kurz, recorded just fine.
I thought I read a post from Jerry about MIDI strangeness after the "fix" for "MIDI chase" or something like that.
Does anyone know which release had those changes?
 

jatoth
Craig, buffers are at 128. Doesn't seem to matter

Just to be sure, are you referring to the audio/ASIO buffer or the MIDI buffer? They are not the same thing.

The MIDI buffer is set to 250ms by default, and lots of systems (including mine) drop MIDI notes randomly or do other strange things with MIDI unless the buffer is raised to 500ms or even more. As Craig says, the MIDI buffer doesn't affect latency. It tells Sonar how far ahead to read data from MIDI tracks, the step sequencer etc. If that buffer overflows then whatever if fails to 'catch' gets dropped or otherwise mangled.

I was referring to the "Number of buffers" = 128 in Preferences - MIDI - Playback and Recording.
Prepare Using XXX millisecond buffers  is set to 1000.
I have done other projects with up to 15 MIDI tracks triggering ext synths as well as VSTi. This is the first time I ever had this problem. This project has 2 MIDI tracks (EZD and the problematic bass track) and 2 audio tracks.
Could my problem be MIDI clock/timing related? I have never messed with the MIDI clock settings, and quite frankly don't know the first thing about syncing MIDI clocks. I never seemed to need to before.