I opened a case with PTC, however this was closed saying it works according to product specification. Let me explain, what I believe is a bug or at least overlooked by PTC. When using config.pro option; Regen_failure_handling no_resolve_mode.
Creo now has the nice option to see in the model tree the errors, these are also listed in the notification center, but this only works in some cases. If you create a simple model of a rectangle with two dimensions in the sketch, let's say Length and Width, then extrude for the Thickness. Assign each dimension to a parameter in a relation; Length, Width, Thickness
If you pass a zero value to the Sketch dimensions, close the relation window and regenerate, the model will fail and show the errors in the model tree/notification center.
If you pass a zero value to the Extrude (Thickness), close the relation window and regenerate, the model will NOT Fail. You will see in the message log that some relations are no longer satisfied, if you open the relations you will see an Invalid left side of assignment.
I believe there should be some constancy in how this behaves, for our business this can be critical, the user has no idea that there is an issue since it's not reported to the Notification Center and the models uses the 'rolled back' value, so to the human eye everything looks ok.