Per target version and platform: how many machines failed to update, and by which cause. A machine counts once per version and once per cause; a machine that failed for two causes is in both rows, so the rows of a version can add up to more than machines_failed.

not_applied is apart from the failures: previous_not_applied are the machines that found the update before this one still staged, by the version they run; staged_not_applied are the machines that staged this target and have no applied for it.

net_probe (lmcp-mac#383) is apart from the versions: what the client's probe of each artifact host role found after a transport failure, by platform and ASN, in machines.