Hi, James,
it helps if the dough does not stick to the baking stone / baking
sheet / tray when you put it in the oven. Sometimes when you invert it
onto the baking stone (for example) a wet spot of the dough will touch
the hot stone and adhere to it for a few moments hindering the rising
of the dough at that spot in the first minutes, causing the loaf to
tear or rise unevenly. You can use corn- or rice flour to prevent this
or bake the loaf on oiled trays.

Also, try spritzing the oven with water (the back and the sides) or
pour about half a cup of water into a hot pan at the bottom of the
oven before putting the loaves in. This will prevent the outside of
the dough to set too quickly. Spritz the oven about 2-3 times in the
first 7 minutes.

Regards and good luck,
Konny