One zoom level not updating

Is it normal that one of the zoom levels (16) hasn’t updated from an edit. This is an edit from a few hours ago.
Should I do anything or leave it?

Leave it.

Assuming you’re talking about mapnik: When it’s very busy, tile render requests get dropped, to keep the server from overloading. A faster tile server for mapnik is currently in the works.

see http://wiki.openstreetmap.org/wiki/Servers/yevaud