I was asked today to weigh in on the potential cause of this apparent damage to a frame. In actual fact, it isn't damage as such.
To explain, we have to consider a critical concept when working with honeybees, the bee space. The bee space was discovered in the 19th century by the Polish beekeeper, Johann Dzierżoń. The idea behind the bee space was the discovery that honeybees will always build their combs so that they maintain a 6-8mm gap between their combs, just enough to allow workers to pass each other by, back to back.
It was this discovery which a few years later led to the invention of the modern removable frame hive by Lorenzo Langstroth, and every removable frame hive is designed to have spacings that allow bees to build combs according to the needs dictated by the bee space.
However, bees sometimes build their combs in a crooked manner. This is especially true when the adjacent comb has projections such as drone cells or queen cells, which always project from the comb and thus reduce the bee space between the combs. As a response to this, the bees may start to chew away the comb on the adjacent frame, to restore the bee space.