Another possibility is that when you have the slow side down the ligero is heating up, but hasn't burned the wrapper yet. Then, when you give up and turn it to the top, the wrapper finally catches on fire.

Another possibility is that one side of the cigar was laying against a more moist surface like a wall of the humidor, or a wetter new arrival cigar.

Or the cigar was just packed too tight on that side, or veins in the wrapper...

Aren't handmade goods fun?