Core:archive hangs for one site


I’m using Piwik 2.17 and I have 3 sites. One of the 3 sites which is not that large (and not the largest) has a problem when I try to archive:

console core:archive --force-idsites=6 --force-all-periods=315576000 --force-date-last-n=1000 --url=‘My url’

It never seems to complete even after 24 hours and I kill the process. My other 2 sites have no problems. Perhaps related - when I view the MONTH view of this site, 4 months May/June/July/August 2016 have 0 hits, but if I switch to week or day view the data is there. Any ideas?