Diagnose error message in MainStage

I'm intermittently getting this error:

An Audio Unit plug-in reported a problem which might cause the system to become unstable. Please quit and restart MainStage.

The support article isn't very helpful, asking me to disable non-apple plugins, because the concert is big:

24 songs each with it's own patch, each patch probably having 2 or three AUs mapped to different controllers. The 3rd party plugins are almost exclusively Kontakt from NI and Analog Lab from Arturia

The error is intermittent, the concert can run for ages fine and then the error occurs out of the blue.

I have used aliases on several AUs that are reused throughout the concert.

Why can't MainStage actually report the plugin that is causing the issue? That would seem to be the most obvious thing.