The digitize counter seems to be off by one (at least in r17054, and at least for the first wanderer). The counter was set at 7 DURING my combat with an assassin, and then decremented to 6 AFTER the combat, making it expire one turn short of the first wanderer's actual appearance.
That counter could just be set to 8, and be right most of the time. But then it would be wrong when used against monsters that don't take a turn (such as witchess monsters, which are a fairly popular target now). This would be handled by setting the counter when KoL actually starts counting (the next time you adventure in a place where wandering monsters can show up, which is basically adventure.php but not places like the shore), but I've been avoiding trying to figure out how to handle that for years.