From what you describe it sounds quite a bit like an over humidification problem. To much humidity would cause a sour taste and would also cause the wrapper to split and pop due to swelling when the heat and humidity mix. The only cure is to take the cigar home and leave it in your humi for about a week or even 2 before smoking it. When you buy a cigar right out of the shops humidor this can happen because not all shops are so great at keeping their smokes proper stored.