In Weave 16, there always seems to be just slightly less units around than necessary to hit the required essence(?) to open the portal. Maybe they’re getting stuck somewhere, but all the times I’ve played it we’ve had to backtrack and hunt down units.
In Weave 24, in the finale arena, two blightstormers spawn and sometimes get stuck off to the far left. Nothing trueflight can’t handle, but a little awkward waiting around for them to show up.