Audio track playing erratically

I am super frustrated so I hope someone here can help. I'm using X1. I've got a project with a few audio tracks and a few midi tracks. I've frozen the midi tracks and I'm trying to export the song to a stereo version.
 
I exported to an mp3 and started listening to it. It sounded fine but then after the first couple of lines, the lead vocal dropped out. I went back and checked the original project and after numerous trials this is what I found:
 
When the file first opens, if I hit "Play" from anywhere the only vocals that I hear on that track are the sections that I processed with "V-Vocal" -and there were only a few short sections. But then, if I stop playback and restart it, it plays just fine.
I tried removing the V-Vocals and re-saved it. Same thing happens, except that even those sections that were originally processed aren't heard until I stop and restart playback.
 
All other audio track play back fine.  Computer resources are fine. It's very specific. Nothing else is dropping out. I tried cloning just that track to a new project and the same thing happens.
 
Any ideas?
 
Doug

No I didn't.  Are you suggesting that I should? Or saying that I shouldn't? Bounce the whole track? Or just the pieces with the V-Vocal? The track is a comp of a bunch of different takes. V-Vocal is applied to 3 small pieces.
 
What I did try, which I never knew you could do to an audio track, is freeze it. That didn't work either.

OK, I tried that. First I tried just bouncing the clip. Then I tried bouncing the entire track. In both cases I could see the waveform. Same thing happens as when I deleted the V-Vocal- no sound at all when I first hit "Play". When I stop and restart it, it's fine.

Thanks for the advice but I don't see myself upgrading any time in the near future. I'll keep trying different fixes; maybe something will work on this project. And in the future I'll be very cautious about using V-Vocal. I'll clone a track before applying V-Vocal, so I can fall back on the original if this kind of thing happens again.

I have never had to bounce V-Vocal clips before exporting. I have had projects with close to 100 VV clips before with no problems.
 
Oh yes - this was also observed on an XP32 system with 4Gb of RAM running Sonar 6PE, so system specs don't really come into it
 
The tried & trusted way is this: before even thinking about MP3, do an export @ 16bit, 44.1KHz in other words, CD quality. Make sure you use whatever dithering algorithm you prefer.
 
Now listen to your export (reimport it into Sonar). If this is fine you can use the export as the basis for your MP3 conversion.