Check the space between the frames with the boxes stacked (much easier without bees on them, eh?)
There are some cases where boxes from different manufacturers don't match and leave extra space between the layers of frames, and the bees will promptly build comb there, usually drone comb.
The real answer to the drone comb problem is to give them a place to make drones somewhere. Best place is the next to outside frames in at least one box, probably two if you have a two or three box brood nest. You can use a foundationless frame, and the bees will build some nice drone comb there, and use it when they want drones. Typically they raise a nice crop in the spring and another in mid to late summer, then use the comb for storage at other times.
This cuts way down on drones in the honey supers, drones between frames, and clumps of drone comb in the brood nest.
Peter