Problem with Voxengo VST3 and Sonar Platinum

Voxengo Elephant 4.2.1 64 bit VST3 and Sonar Plat not playing nice together:
(Inserted on the main buss) Sometimes I get no audio out of Elephant and the output meter is pegged in the red like it is oscillating.
Also get that DC offset "clunk" sound when starting and stopping the transport.
If I put it on a mono channel it almost always does the above. If I switch the channel to stereo the problem goes away.
If I use the 64 bit VST2 version of the plug the problem does not occur.
 
Anybody else have similar Voxengo VST3 problems?
 
I posted on the Voxengo board but Aleksey said he could not reproduce the problem.
 

I'll try this evening and post results back here. Thanks.
 
Update: No I cannot reproduce it with a single track, single instance of the VST3.
It seems to only occur on a full sized project with lots of plug-ins.
I'll keep an eye on it and if I get any more hints of what is happening, I will post here.