A few people have written to say that they haven't had any problems with the Pierco frames, so I'm still at something of a loss as to why I'm seeing the patterns I am (and, in response to a suggestion posed in a comment, no there wasn't a grease patty or leaky feeding jar above that build out pattern on that frame). I did, however, come across this article from Bee Culture magazine on Pierco frames. It notes that because the plastic frames fix the cell size to what works well for breeding workers, rather than the larger drones, the bees will sometimes have to go to extraordinary lengths to find a place to lay their drones. Maybe this is what they were doing on my frame?