From earlier lessons you'll have noticed me ignoring the small split - called a 'shake' - that appeared very early on, even though the timber seemed well air-dried. Splitting like this is difficult to predict, though its fair to say that the bigger the piece of wood (the more of a block), the more opportunity there is for internal pressures to open up fibres.
So what to do? In this lesson I'll give you various options and show you my solution: inserting wedges and re-carving the surface. Be sedulous in matching the grain and positioning the wedges and you'll have anything from a repair which is innocuous to one that's invisible.