I've had the same problem. When the humidor gets full you're trying to humidify a lot more cigars and they absorb the moisture. After a week or so it should settle in. If it doesn't, you may need to add another humidifier, humi-pack, or the gel type humidifier in a jar.
However, there is a fullproof, always works solution to your problem... Select five fellow forum members, remove 20 of your best cigars and send 4 to each of the five you selected.
So, what's the problem?