This is an example of a too thick of a coat or dries too fast locking in the water in the product this will show in the first 24hrs.

You will get little volcano looking cracks this is from the water in the product trying to escape as the coating dries.

Solution: Apply no more than 5-10mil per coat. (Latex house paint goes on at about 2mil)

To fix cracks sand the high spots and reapply multiple thin coats.  If they are deep cracks fill with a mixture of the crumb rubber and the Dura-Rubber.