It doesn’t take rocket science to understand that rockets eventually have a success rate of less than 100% .
(Edited changed failure rate to success from child comment)
That is true, but it is not directly related to this issue. SpaceX doesn't (can't) reuse second stages. (For now.) The one in question which had the anomaly was a "brand new" second stage.
It is more likely that either this is due to a defect which escaped their QA, or a design issue with a very low probability rolling a nat-1 this time, or some change they introduced not working out as they expected. I would not describe any of those as "aging".
