Test for double in size using the finger-tip test. Insufficiently risen dough can crack. The oven may not be heating evenly. The bread will crack if the dough was dried out before baking. Some cracking on the side is appropriate.
All bread expands in the oven causing some cracking.
Excessive flour can lead to a cracked top. Reduce the flour used in kneading and shaping. Do not cool bread too quickly or in a drafty location. Dough that was under-kneaded cannot maintain its shape properly. Follow recipe directions for kneading .