I was doing an inspection today and saw on one frame that there was an area where several empty brood cells had merged, like maybe their walls had broken down making an open "pit" in the comb about the size of a nickel.
I would hope the bees would rebuild that area, but I hadn't seen any mention of it on this site. Just wondering if it's normal.
Could be an area where a queen cell had been at one time, I see this in feral hives a lot. This is my guess at what you are seeing.
...JP