Reason I asked was because they have cracked down (supposedly, I haven't seen it first hand) on abuse of the API and wondered if that might be a factor.
Do you have any log access? If so, are the sitemap and new articles being crawled?
I don't work in that vertical so this is all hypothetical, but I can't see a reason to regularly crawl more than what the actual new content is in true news. I'm wondering if that is a recent change that you're seeing and if logs correlate.