Is the member-join event different from user events?

[Bryan Robert]

I've been facing issues where the nodes in my cluster join each other, but the member-join event is not triggered consistently for all nodes. serf members command shows that all nodes are connected (say 5 nodes, but the member-join event only fired 3 times). I proceeded to make my own 'node-join' user event fires just after nodes join each other, this solves my problem. But I just want to know if and how member-join differs from normal user events.