Finding cracks in your pressed cheese may mean the pressure was too light during the pressing process and the curds have not moulded together completely, causing those undesirable cracks on and within the cheese.
You can try increasing pressure and pressing time.
Additionally it may be because your drying environment does not have high enough humidity. The rapid dehydration causes shrinkage of the outer surface and cracks form. If this starts to happen you can place a wet paper towel in the base of your cheese maturing box, place the cheese mat on top, add your cheese and seal. This will allow moisture to be absorbed back into your cheese and hopefully heal the cracks.
If mould begins to form in these cracks, you can try spraying brine into the cracks with a spray bottle to flush the mould out, but you must to ensure that you dry the cracks out thoroughly after this process, because excess moisture may encourage more mould growth. For this reason, you should not spray out any really deep cracks.
If mould growth isn't a problem then it's just a visual issue. The cheese will still taste just as good!