If they’re going to crack it pretty much has to start at the surface, so magnafluxing should reveal any existent cracks. However, if there is any question at all about the condition of your fulcrum pins I’d get some new ones from a reputable source such as Doug Jennings (for stock size pins) or Dale Akuszewski for the oversize pins. Consider them a wear item… after so many flex cycles they’re going to go.