If they're smoking well, then humidity may not be your issue. However, non-uniform humidity might be. For example, if you move some sticks stabilized in a drier environment to a more moist environment this can make one side of the cigar more moist than the other, particularly if it only spends a short period of time in the new environ. The solution to this is to let the cigars acclimate to their new environ for a week or so.
Alternatively, have you felt the area ahead of the tunneling for a soft channel? In properly humidified and equilibrated cigars, the most common cause of tunneling or runs is a channel that is more open space than the rest of the cigar. The wrapper and binder over this channel burns ahead of the rest of the burn zone, resulting in a run. There is no solution to this problem except perhaps heavily dabbing the area ahead of the run with saliva.
Wilkey