Quote Originally Posted by RicaRuin View Post
However, it doesn't seem to respawn when it failed. Joined an instance where Castrum spawned but was abandoned fifteen minutes ago, did some skirmishes and CR to pass time.

For the next 100 minutes, Castrum did not respawn, but there were a lot of 10+.
It does

Was in an instance yesterday when Castrum failed due to not enough people entering. Instance started and everyone just left. An hour after it closed Castrum popped again

If your instance is locked though, Castrum will no longer spawn