Hi,

Maybe I can give some clue. From time to time, System Modeler gets better at detecting singularities during build. Such development is often introduced as a measure against problems affecting simulation in earlier versions. Sometimes – possibly what is seen here – a model may have been able to simulate with acceptable results in an earlier version despite presence of model singularities, but the quality of such simulation results cannot be guaranteed.

In my bug-hunt I found something strange, I have a sub-system that when validated in SM 13.2 returns:

If this is a sub-system which is not meant to be simulated on its own, it is not a problem that it is not globally balanced. The difference between being reported as an error or not might be due to some change in the classification of whether the model is expected to be usable on its own. Maybe the model has an experiment annotation despite it not being intended for simulation?

Finally, a general recommendation for how to approach the problem would be to look into why some equation systems are so big. Generally speaking, models that work well don't have equation systems of these sizes. However, there are exceptions, for example when the torn size of the system is small. Smaller equation systems not only make the model faster and more reliable to simulate, but also makes it a lot easier for the user to understand and debug.

But how do I know a suitable size? My model is really big and very complex, it has electrical and mechanical domain.

There is no general answer; within any domain there are applications for models of different level of detail and complexity. How to select the right level of complexity for the task is something to be learned by experience, and is a key aspect of becoming a good modeler.

NOTE: Sorry, I replied to myself but should be to you. I don't know how to delete.

Obviously me neither.