It turns out she wasn't quite ready for release after all.
I knew if I waited long enough the full answer from Ed Clark would show up on their chat...
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Source Ed Clark, WCV: First, NX is in great health. She is strong, fit, able to fly well, eating well, and everything else she needs to be at this age, from a physiological point of view. What became clear, only at the release, is that her behavior, which looked fine under the controlled circumstances of the flight pen, was a bit more juvenile under stress than we would have imagined, given her interaction with her siblings. When they approached her on the ground after her initial release, instead of responding with an adult "one step closer and I'll rip your face off" vocalization--the kind we got from NZ and NV--she gave a juvenile distress "cheaping" call. In and off itself, that would not have been a huge deal, but her response to the people was to hunker down and run, rather than fly off.... again, a juvenile reaction. It was a normal reaction, entirely, but a reaction of a bird who has not quite "flipped the switch", as Dr. Miranda puts it, to being a fully mature sub-adult. So, since there were so many people there, and we knew that someone would not be able to resist approaching her, we decided that it would be best to bring her back and give her a bit more time. Part of the benefit of having KS in the cage with her, is that it is giving her something with which to deal that makes her respond... Again, normal stuff, but pushing her a bit... That is allowing us to watch and monitor her reactions.