I've got east west strings in play 64 engine in sonar x3; it sounds fine in the sonar, like strings.  If I go to mix them down, or the song, the strings hit the initial note and then shut off, almost like on a keyboard if the sustain pedal is off.  Like I say it sounds perfect in the sonar environment, it's only when I go to mix them down or bounce them to audio.  Does anybody have any idea why this is happening - is there some output issue I have to deal with from the play software?  I don't understand why it sounds fine in the sonar and then shuts off when mixed down - help is appreciated.

Try bouncing them down in a realtime, audible bounce. Change the freeze/bounce options to audible bounce, fast bounce box Un-ticked. QLEW has never PLAYed nicely with Fastbounce.

It's a Play issue.
In Play, stream the samples from memory rather than disk and you should be fine.
Fast bounce works fine too if you stream from memory.
(My Play libraries are on an ssd and I get the same issue you exhibit but changing the streaming location fixed it for me)