Some of the sourcewells on Ember Isle seem to be bugged. The center Defense Arch is missing and cannot be upgraded. The turrets and lifesprings can be upgraded but no planar invaders spawn making it difficult or perhaps impossible to complete the daily onslaught quest.

I checked several of the sourcewells and the ones where I found missing Defense Arches were at:

Fell Fields
Forlorn Fen
Gilded Strand
Stranglewood

I'm not sure if this may or may not be related to the Hellbug Event. Yesterday I saw an announcement "[Unnatural Speciation] has started in Ember Isle on Vigil" in chat. However, when I went to Ember Isle there was no event posting with objectives above the quest stickies on my screen as would usually appear. There was also no glowing symbol on the zone as is usual with zone events. There were Hellbug Rifts that spawned in several places. Thanks in advance for looking into this.