Beste antwoord door John de Jong
For your two travels Nijmegen - Leiden, you expect to have a quick connection in Utrecht, but this is not an official connection. It does not appear in the NS Travel Planner. In other words: if you manage to change trains in Utrecht very quickly, you are just lucky, but normally, to catch the 14.23 Utrecht-Leiden, you need to leave Nijmegen with the 13.12 service (direction Den Helder), not the 13h27 service (direction Schiphol). So both times, you were on time and not late.
When you check the Travel Planner you will notice that Nijmegen – Leiden is sometimes quicker via Schiphol. You are allowed to take this route when it is shown in the Travel Planner.