Siempre la clarldad viene del cielo;
es un don; // no se / halla entre las cosas
sino muy por encima, y las ocupa,
haciendo de ello vida y labor propias
I've bolded the clashing stresses. 6 and 7 in the first line; 6 and 7 again in the 2nd, then 9 and 10 in the fourth. It's true that the preposition entre doesn't have a strong stress, but it's stlll a mouthful. Odd-numbered stresses are just normal variations when they occur on 1 and 3, but on 5, 7, and 9 they create a much more irregular effect, because they clash with the stresses on 6 and 10 (or sometimes 8).