My buddy posted a nice picture of a frame full of brood with scattered cells missing along both vertical and horizontal wires, some more than others.
If the wire is exposed in the bottom of the cell either the queen won't lay in it or the bees remove the egg (or larvae). Probably next round they will add some wax when they clean or the wire surface will oxidize enough they ignore it.
Looks pretty strange, but I don't think it hurts anything, and once the comb has been used a bit they stop skipping those cells.
Peter