I use the same method and what I have noticed is when the egg box humidity and the incubator humidity are way different (as your seems to be) you get more condensation inside the boxes (probably due to the surface of the plastic inside/out being different temps (as carried by the moisture)

So my recommendation is to add an open box/bucket of water to the incubator to help drive the overall humidity up...this is what I do and my condensation is much lower.

Hope this helps.