When a Clash is set to "ignored" it stays in this status until a user set it back in an aktiv status. So if the Modell changes, this clash does not reopen. This can cause Problems because a ignored Clash of 2mm kann be a big clash in cm-Spaces after the Objects has been changed. So the Clash should be reopened automatically. If don't, there is not only the Problem of not recognizing the bigger clash but that you can only check the situations after manually reopen the Clash. That is far from user-frindly an is a potetially source of error.