Right, my findings so far.
 
It works as it used to with Dim Pro
It doesn't work with Rapture Session
 
I'll keep testing, though it won't be for several hours

I'm getting unchanged odd results with Roland TTS (DXi), FM8 (Synth) and DimPro (Sample player).
 
The drag action does however cause fades or crossfades if I'm not careful.

brundlefly
Try splitting the Instrument track first.

This does work, both drag move and drag copy, but it still has the buggy behaviour of unfreezing a synth who's had it's audio stolen.  This behaviour gets worse with each interation of move/unfreeze.  So the fix, if there was one, was questionable and addressed only half the problem.

Bristol_Jonesey: I can't get Dimension Pro to work . . .
 
Brundlefly: This works, and it will be a useful workaround for bouncing individual kit pieces in, say, AD2. But for a single bounce softsynth copy/paste is still as efficient. 
 
Paul P: I have not experienced any buggy behavior when using this technique, and I have been doing it for a long time! Perhaps your compositions are more intricate than mine ;).
 
Thanks everyone for your responses! I have never had much luck with forums, usually just answers like 'I don't know' (then don't waste my time!) but I believe Cakewalk users are the most knowledgeable and helpful out there! 

Due to this being buggy there is now no way to change the render bit depth of soft synths after the initial project setting.  Changing the render setting in preferences has no effect on bounce to track (broke in Sonar 2015).  The workaround was to freeze the synth and drag the track.  Must nearly be time for a nice fat bug fix update. 

tenfoot
Due to this being buggy there is now no way to change the render bit depth of soft synths after the initial project setting.  Changing the render setting in preferences has no effect on bounce to track (broke in Sonar 2015).

The conditions for this issue still need clarification as I was not able to reproduce a problem other than that the project needed to be closed and re-opened for the render depth change to take effect. When last we left it, I was speculating that your case might be synth-specific, but that was never confirmed. For the benefit of others following along, here's that thread:
 
http://forum.cakewalk.com...to-track-m3374413.aspx
 
 

ttaggart4
Paul P: I have not experienced any buggy behavior when using this technique, and I have been doing it for a long time! Perhaps your compositions are more intricate than mine ;).

It's not the move per se that causes the problem, it's the subsequent unfreezing and re-freezing of the synth that is problematic.  Maybe you don't do this ?  Watch was goes on in the transport window when you refreeze after having stolen the clip from a frozen synth and then unfrozen it.  The first time it will go through 2 freezing passes.  The next time it's 3, then 4, etc.  And often the resultant clip get longer and longer each time. 

Paul P

ttaggart4
Paul P: I have not experienced any buggy behavior when using this technique, and I have been doing it for a long time! Perhaps your compositions are more intricate than mine ;).

It's not the move per se that causes the problem, it's the subsequent unfreezing and re-freezing of the synth that is problematic.  Maybe you don't do this ?  Watch was goes on in the transport window when you refreeze after having stolen the clip from a frozen synth and then unfrozen it.  The first time it will go through 2 freezing passes.  The next time it's 3, then 4, etc.  And often the resultant clip get longer and longer each time. 

I do exactly that. When I am ready to mix AD2, I 

1. Solo a drum kit piece
2. Freeze the synth
3. Copy the resulting clip to a new track solely for that kit piece's audio
4. Unfreeze the synth
5. Solo the next kit piece
6. Lather, rinse, repeat

I know there are ways to assign individual kit pieces to their own audio tracks, but I find that tedious and unreliable. I have not encountered the issue you mention, e.g. bugginess of this process.

I do exactly that. When I am ready to mix AD2, I 

1. Solo a drum kit piece
2. Freeze the synth
3. Copy the resulting clip to a new track solely for that kit piece's audio
4. Unfreeze the synth
5. Solo the next kit piece
6. Lather, rinse, repeat

 
 
This may be where we're not connecting.  I've only seen a problem with Move.  Copy works fine (or at least it did).

brundlefly

tenfoot
Due to this being buggy there is now no way to change the render bit depth of soft synths after the initial project setting.  Changing the render setting in preferences has no effect on bounce to track (broke in Sonar 2015).

The conditions for this issue still need clarification as I was not able to reproduce a problem other than that the project needed to be closed and re-opened for the render depth change to take effect. When last we left it, I was speculating that your case might be synth-specific, but that was never confirmed. For the benefit of others following along, here's that thread:
 
http://forum.cakewalk.com...to-track-m3374413.aspx
 
 

I have tried tried this on every vst synth I have.  Yep.  It's certainly broken, and restarting the project or Sonar doesn't fix it.