Even when the blade is newly replaced, it catches, not leaving a clean cut. Rarely can I get a slash that is deep enough to facilitate good "oven spring." In fact, I often feel like I'm damaging the dough, as I end up hacking away at it, which I suspect may be adversely affecting its structure.
Is it a problem with my dough? Is it overproofed? This happens with 70% and greater hydration loaves, which I generally let rise in a banneton. I use the "Tartine Bread" book's method of turns and folds, with a levain created using the instructions from the same book. I'm meticulous about weighing the ingredients, and I am careful to shape in the way prescribed, to create the "surface tension" (apologies to the chemists out there) that is recommended.
Your help would be most appreciated. Thank you. ;o)