It might be because Middle C sits right on top of a domed screw hole, possibly overtightened in production? Don't know if those were done by hand or by machine. Just speculating.
I'm guessing it will hold up fine. Key-up pressure from the spring is not that intense. And I dabbed at the glue as it was drying, and it had picked up some black pigment from the plastic, bonding well.
I peeked at a few more keys and the bumper assemblies seemed fine.
Sometimes, returning things is more of a pain than its worth, as long as the kludge works well and is not cosmetically distracting. Looks and plays like a champion at day 3.