As the cigar burns, some of the oils build up ahead of the "cherry". On cigars with a higher moisture content (whether due to ligero leaf or high rh) you tend to get an off flavor at times. I will purge with a lighter at the foot until it can burn on its own and continue purging until the flame goes out. Sometimes this can take up to about 20 second (especially if I'm relighting). Once the purging is finished my sticks will taste better and will generally burn better. I find that this works for heavier smokes that I'm smoking too slowly on or relighting sticks that have gone out.
But then, that me. YRMV....