Hello,
 
I have Sonar Platinum with the latest (August 2017) update.
 
When exporting to audio, my Vienna MIR Pro (Impulse Response room) loaded in the FX is missing in the audio file for the opening but then 'kicks' in a little later. I have tried both with and without fast bounce and have tried different file bit depths. Typically, the FX is missing for between 10 - 20 seconds or so in the audio file but then 'appears'.
 
I should mention that Sonar plays back perfectly, it's just when saving to an audio file that the problem appears.
 
I have never had problems with this before and have been using MIR Pro for a few years now and it has always worked to perfection in Sonar.
 
I have Windows 10 and my system is based on an Intel Quad Core i7 4820K Processor with 32 Gig of DDR3 memory so there is plenty of support available there and, as I mentioned, everything was absolutely perfect until now.
 
I'm thinking / hoping there is some setting somewhere and would appreciate any help with this.
 
Thanks.
 
 

I would first restart the computer and make a new test.
I also would test what happens with "plug-in load balancing" disabled and enabled.
If this doesn't help I would make a small project for testing with only one track and Vienna MIR Pro. To see if there is a general problem with one of the components.
 
 

Try moving your project to a later starting point.

THambrecht and Greg,
 
Thank you for your replies and suggestions. Unfortunately the problem persisted.
 
Eventually I uninstalled Sonar completely, cleaned out my system then did a fresh, clean install. That seems to have resolved things at the moment and I am able to export to audio with everything intact.
 
So, it's all working .. at least for now.