Q:

How to troubleshoot the warming "Causes instability in matrix" in a gap run?

R:

One of the test cases we have seen for this warning is that the version of SACS was 16 or below. When the same model is run in V23 or above, the warning is resolved.

The background of this is that during the upgrade from V16 to V23, the solver compiler is upgraded to cater even small differences in nonlinear convergences. Due to which you will see a very minor change in results as well.

So, if you want to avoid this warning, please upgrade the version of SACS.

Otherwise, even with that warning also, there is not too much difference in result, and you can continue working on that.

With the recommendation provided here, if the warning persists, please raise a Service case and share your model files for our investigation.