On 2 different runs (1x Grade 3 / ADV + match and on 1x Grade 2 Free Match) The Castrum Demonica stopped responding.
On the first 2 screenshots, that was a Free match (Grade 2 // 55 Eqv). We had destroyed the Arx Demonica, killed the core, the Castrum repelled us, raised the shield, and started the bombardment script. The Castrum Demonica continued to visually animate and kept firing finger lasers and random bombs for the rest of the duration but only the first wave of mobs spawned. I did notice the indestructible missiles stuck in Orange Tower.
The second instance (last 2 screenshots) was in a Main ADV match. We had dealt with 2x Buster waves, destroyed the Arx Demonica (to the point the wall actually shattered, but upon running up the steps, the door was locked and the usual courtyard mobs had failed to spawn. This time the Castrum Demonica was completely inanimate.
Also as an aside, there is a typo in the system announcement for the Fellwyrm. If you rout an enemy, as in to mean fleeing the field of battle, it is spelt like that, not "route", however, such units could be referred to as "having been routed". But route in the context given is wrong.