Something wrong with an array component's sheet: what to say, and what to point at. The message says WHAT IS NOT ALLOWED and stops. Why it is not allowed belongs in the documentation - a user reading an error is trying to fix a sheet, not to learn the design of the feature, and a sentence of reasoning after the fault buries it. Components are what the simulator highlights in red, so a problem names the ones a user has to look at. Empty only where the fault is the sheet's own settings and no component is at fault.