Welcome to orchidboard!
Cracked roots are nothing to be concerned about. It happens very frequently and has no ill effects on the plant. The cracked part is actually the outer layer of the root, called the velamen. The velamen is a rather thick layer and acts as a sponge to hold moisture and transfer it to the true root, which is the thin wire like bit in the center of a root. The velamen does not need to be intact nor pretty (is also often stained/blackened/shriveled in places) in order to fulfill its role.
Roots will also tend to crack when repotting (they don't resist well to bending) so one trick is to soak the plant in water for at least 10-15min before repotting. This makes the roots more pliable and less likely to crack.