I have a MainStage Concert on my 2019 MBP (Intel, OS 13.2.1) with multiple instances of Kontakt 7 (AU).
When the Mac is online (Wi-Fi enabled), the Concert opens immediately and works perfectly. However, when the Mac is offline (Wi-Fi disabled), the Concert crashes while loading. If I then relaunch MainStage and open the Concert again it loads and works as expected. Second time's the charm...
It seems clear that something in this Concert doesn't like it when the Mac is offline. I suspect Kontakt 7 because that's where the crashlog seems to point (see attached). But I'm not an expert in reading logs, so I can't be sure.
This is frustrating because theaters don't always have reliable internet, and my anxiety goes through the roof when I see MainStage crash right before a show.