I know this issue has been in Sonar for a long time, but it is getting annoying now.
 
Basically, whenever I move the Now time to a new position, I always have to press the SB multiple times to get everything to play back properly. More often than not, most tracks won't play back at all the 1st time I press the SB. Or they would play back out of sync or even play the wrong MIDI notes.
 
This problem is also very noticeable when working with Dim Solo. In that case I don't even have to move the Now time. Just stopping after some amount of playback and the pressing the SB once will cause almost all other non-soloed tracks to not play back at all, just the soloed track. Then I need to press the SB multiple times to get everything to play back properly.
 
Not sure if it is related, but sometimes doing something simple like muting a completely unrelated track during playback will briefly interrupt MIDI for all other tracks. Or simply highlighting a MIDI track during playback will interrupt other unrelated MDI tracks.
 
Maybe also related... Pressing solo on a track with Dim Solo enabled will briefly interrupt MIDI data to all other tracks even though they should continue to play, just at a lower level. Why does the MIDI data get interrupted at all?
 
Do other people see similar issues?

I've never seen this issue...
 

Yeah I've had it happen.  Usually for me the midi drums (doesn't matter which VSTi) will start out of sync, but I've also had audio tracks not play or out of sync as well requiring stopping and starting play. It is annoying.
 
Dan

I've had issues like this before. Sometimes I'll hit play and certain MIDI tracks aren't playing until I stop and start again. Every now and then, I will unsolo something (audio, MIDI whatever) and it will send some seemingly random MIDI notes to a completely unrelated synth track. I've never been able to pin it down to the point where I could file a bug report, however.

Oh and I almost forgot...sometimes I'll have odd things happen with Geist's song sequencer when I toggle Sonar's loop mode on or off. It makes Geist think we're further along on the timeline and it will start playing patterns that aren't supposed to play until many bars later. Again, I cannot work out a recipe to file a bug report.

OK so it is not just me.
 
BTW I think this might be related to (or made worse by) having VSTis sending MIDI data out. Unfortunately I've had great difficulty in the past getting CW to look into bugs that require any 3rd party plugin to reproduce.

No wonder I like Sonar, I don't have these things happen to me...the closest I've come is where a MIDI instrument didn't play back when I started playback, but then if I just put the now time before where the part started, then it would play back. I sure a lot of times it was retaining a controller 7 = 0 but I'm also sure some times it was not. But this is very rare in my setup.
 
What happens if instead of using the space bar you click play on the transport? Do you have to click on it multiple times? If not, then it seems the problem would like between the communication with the QWERTY keyboard and Sonar. What happens if you connect the keyboard to PS/2 instead of USB? Is the keyboard wireless? Etc.
 
If you have to hit the transport playback button multiple times, then that's something else altogether but it would be useful to isolate the conditions under which this happens with more detail.
 
However, the "out of sync/some tracks play some don't" issue implies it's more than just about starting and stopping playback. I have a feeling the sync issue is where to look for problems and fixing that will solve the space bar problem, rather than the other way around.
 
Try increasing the latency and see what happens...long shot, but I think it's time to collect data on what doesn't solve the problem to get a better idea of what might. Bear in mind that if I haven't experienced a problem, then I'm pretty much reduced to guessing at what it might be.

Keyboard or clicking Transport doesn't matter. Has nothing to do with latency, my latency is set to 1024 when I'm mixing. Stopping and restarting playback is the only thing I've found to correct it. I've also had the midi instrument not play, I don't have to move the now time, stopping & restarting playback fixes that as well.
 
Dan
 

I have had this happen and when I close and reopen Sonar it usually starts working better. It is almost like its not able to respond to the keyboard presses in a timely manner. I also see sometimes when the midi plays but is not in synch with the audio.  I push stop and then play and it works the second time usually.

I have had delays in the past when pressing play on my MCU but I can't say I had what is being reported here happen. The delays have gone away since X3 came out.

Sounds like audio interface drivers/firmware to me. Perhaps midi buffers. Maybe a plugin disturbing the force...