Comment 7 for bug 1786261

So, I've noticed something else that may be relevant. My work's configuration actually has two DNS servers, which show up like so:
installing DNS server 10.10.0.8 via resolvconf
installing DNS server 10.10.0.2 via resolvconf
However, I saw that there was some probability that it failed after either log message. In addition to that, there is a "leftupdown" script that makes an _additional_ call to resolvconf to setup the DNS search (and tear it down afterwards). I also (sometimes) locks up at these times, so I disabled that script and noticed more successful runs.

So, suspecting that the problem was with resolvconf I downgraded it to 1.79ubuntu8. That didn't do the trick, but these days resolvconf is managed by systemd - so I then downgraded systemd to 234-2ubuntu12.1 (except for a conflict with netplan.io, which I ignored). That "worked" in an interesting way, now it reliably connects and finishes - but sometimes it takes about 10 seconds to complete each resolvconf transaction.

Based on this, I suspect that the issue is actually somehow in calling resolvconf (if I call resolvconf in a terminal then I don't see a lockup).