We've been noticing this lately on our mirrors too and we sync upstream to CentOS's primary mirrors. For example, this morning we got dozens of emails such as these:

Not using downloaded epel/repomd.xml because it is older than what we have:
Current : Sun Aug 16 00:47:07 2020
Downloaded: Sat Aug 15 00:25:46 2020

Unfortunately, I don't have information on which mirror we pulled from before the time this was run but I can probably update our scripts so we can track this better. I suspect there might be an issue with one or more of the upstream mirrors not being in sync sometimes. I wonder if this is related to the other thread I started regarding centosv4.centos.org being slow for us.

On Fri, Aug 7, 2020 at 6:36 AM Fabian Arrotin <arrfab@centos.org> wrote:

On 30/07/2020 03:05, Mason Schmitt wrote:
> Hello,
>
> I'm seeing issues with stale content from mirrors that are listed as
> being up to date at https://mirror-status.centos.org/
>

Which basically checks the main root of the content dir and then
displays that page.
Not shown on that page is the result of the crawler process *then* only
verifying *all* repositories metadata and comparing with local cache

Normally , assuming that you don't have other internal caching
somewhere, it should get the list of validated (and still to be
considered current) mirrors.

--
Fabian Arrotin
The CentOS Project | https://www.centos.org
gpg key: 17F3B7A1 | twitter: @arrfab

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