This is more common than you might think. I have encountered cheap home routers that have dumb dns proxy caches on them that simply cache everything for a fixed

This is more common than you might think. I have encountered cheap home routers that have dumb dns proxy caches on them that simply cache everything for a fixed time period. I heard of one that simply flushed its cache at the same time every hour. You find out all sorts of bad DNS behavior when you run anything CDN related.