Bread-Bakers v106.n017.7

Usually I score my sourdough or rye breads after they proof, right 
before baking. Recently I have had a number of breads crack during 
the proof. The cracking makes a huge gringe but is sometimes 
misshapen. Does anyone know why this is happening and a solution to 
the problem? Is it too much hydration? Too little kneading?

Lloyd