does it look like a sultana split. It sometime can be caused with to much or to little water. Or in some cases the wather when it gets to hot. .

Usual cause for Fruit Split is erratic water supply - the fruit forms, not enough water, then there is water and the fruit grows too rapidly, because it can now there's moisture, and the skin splits. When the fruit initially forms, its important to keep up a good and regular water supply for even swelling and ripening of the fruit.