Sorry it wasn't much help. Thought it might be a long shot. Apple has definitely changed something in the past couple of days at the back end. Noticed on both my iPhone (iOS 11.4.1) and iPad (iOS 9.3.5 - it's an old 3): When I hit "update everything" in the App Store, only the first few start updating as normal (if lucky). The rest used to go into sort of a holding pattern waiting for the first few to finish downloading/install. Now they just bail out and revert to an Update button. Sometimes you even have to hit the Update button a few times before it takes. Very strange. That aside, since we may have eliminated a local issue, the problems you're seeing could be something going on with Cogent, upstream from your gateway. I know that Level3 (my gateway provider) often has weird, erratic slowdowns to Microsoft's CDNs. Could be that Cogent is similarly allergic to Apple.
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