It's been multiple times and the harbinger boss isn't recoverable after the fight.
Its not bugged, it's just pure RNG whether you get it or not (Also its seeded so you only get 1 chance per playthrough. (I think, its a vanilla mechanic))
uh... is this how you want it to function or just how you've gotten it to fight? as you can make it a guaranteed recover.
Yes. The Hollow is a guaranteed recovery, the rest are not.
Also , does the boss (phase ship's) once defeated are supposed to stay as automated ship or became crew ship? Because after I recovered them, they are still autonomous ship and the game doesn't allow me to restore them ( this ship usees engineering techniques beyond the current state of the sector and can not be restored) which is the same problem I have with XIV sentinel ship. But if I use console command to add those ship , they are crew ship and can be restored after being disabled.
Yes they're Sentinel automated, which makes them quite overpowered, not being able to restore them is a very intentional downside.
(Also to make a ship Sentinel automated takes some extra scripting so you can't just spawn them in)
It may has been reported but is it normal that frozen heart is destroyed after beating the Star fortress?
I cheated by adding marines via console command ( plus 10 phantom in fleet ) to get all the blueprint and at list 40000 marines died ins the raids
Raiding Frozen Heart is borderline an exploit so it costing 10k marines is what's keeping it in check, so ye it's intentional.
Also , I hope the eternity boss AI will get improved because it always crashed on my ship due to overload and it's ship system.
Sadly there isn't much AI can do to improve the AI further without writing something entirely custom
