A slur must clear every intermediate notehead under its span, not just its two endpoints

A slur arcs from its first note to its last note and must stay clear of every notehead (and stem/beam) IN BETWEEN, bulging further out when an intermediate note is higher (for a slur above) or lower (for a slur below) than the endpoints.

A slur spanning a scale passage with a high passing note in the middle is drawn as a shallow, nearly-straight arc that clips through that middle note's notehead.

Gould, Behind Bars, ch. 'Ties and slurs'; Ross, The Art of Music Engraving, slur-shaping section giving explicit sag/bulge rules relative to the highest/lowest intervening note.

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.