Hello Jerm,
I experienced a problem with my last Metro project (a while ago) when expanding the sub sections in the main section. Many of my sub section virtual instrument tracks would not be there after expanding. I was working with with about 5 to twenty virtual instrument tracks on five sub sections and also I was speeding up and slowing down the tempo in the first sub section. I ended up rendering each of the subsections or sections as separate master tracks and then splicing them together. It was a daunting solution to say the least because editing the mix of one section would alter the mix of all the other sections. The activity monitor was showing fairly moderate cpu and memory usage.
I'm not sure what was going on. Would it be better to render the sections to audio before dragging them over to the main section as sub sections when I end up with a lot of virtual instrument tracks in a project.
Phil