We had two versions of varnish in buster-wikimedia: 6.0.8-1wm2 in component/varnish6, and 6.0.8-1wm1 in main. Four new cache hosts, cp[4033-4036], were installed on Friday October 29 (T290694), and at that point component/varnish6 already had 6.0.8-1wm2 having been uploaded on October 26. However, the newly imaged hosts are currently running 6.0.8-1wm1, while I would have expected them to have 6.0.8-1wm2 instead.

We install all relevant packages with the following in profile::cache::varnish::frontend

apt::package_from_component { 'varnish':
    component => $packages_component,
    packages  => $packages,
    before    => Mount['/var/lib/varnish'],
}

$packages_component is component/varnish6, so my suspicion is that either: (1) we install varnish somewhere else than the above, or (2) there's a bug in apt::package_from_component.