This happened to me a couple of years back costing me a good chunk of money in lost sales. My hygrometer was reading 68 steady, it had new batteries, and the works. I went out on the road for three weeks to return to a reading of 65%. I picked out a cigar and it felt hard. It was also harsh when I smoked it which indicates long term dryness disorder. So, I purchased three more digital hygrometers, and checked them against some cigar shops readings. When I took them home they read 49%. So, I cranked up the humidity and tried to revive them but that is when they cracked. I think what happens is that when cigars dry they shrink a bit, and when you re-humidify they expand causing the cracking. Some leaf will dive you more room to navigate like broadleaf, but Indonesian and Java etc seem to be fragile. Overhumidification will also produce cracking at the ends from the swelling. Heat is also a facot that likes to eat up your smokes. Like a credit card on the dash board in AZ, a cigar in the cello in a high humidity/heat situation like your car will put an end to any use of your smoke. Good luck.