Seems to have returned. Looks like sl-security repo.
repodata/updateinfo.xml.bz2 timestamp goes from 1472831996 to 1472837835.89.
Looks like the floating point issue. Some tool is writing bad timestamps.
/etc/cron.daily/0yum-daily.cron:
Not using downloaded repomd.xml because it is older than what we have:
Current : Fri Sep 2 09:59:56 2016
Downloaded: Fri Sep 2 09:59:55 2016