There’s not really any explicit support for AudioSuite in the JUCE AAX wrapper. From looking at this thread from a few years ago it looks like it just sort of happened without us adding anything, hence why it may not work correctly in some situations like the above.
As you’ve done quite a lot of work with AudioSuite do you guys know if there’s a reason why the output channels aren’t being passed to the plug-in? Is this documented anywhere?