I'm comping a vocal using the take lanes and the solo tool.  On one clip the solo'd part sometimes will not play.  If I export the audio, it's there, and sometimes it will play in the project, but mostly not.  Seems like if I use the solo button on the take lane it will then play, and then if I un-solo it it continues to play. 
 
I've tried adjusting my ASIO buffer settings, and played around with a few other things but no joy.  I have a fast machine with lots of RAM so I don't think it's a processing issue.
 
John

There does seem to be an issue with  the Shift Space bar  soloing a take.
There are some takes it works fine on and other that get in a confused state.
I have not quite nailed down a repeatable scenario to what causes it yet, but I have seen it several times today.