Problem with them being locks:
The final cutscene of the game is pretty explicit about the fact that the Knossos tech allowed them to get back to Earth.
i mean if the portal can create a subspace node, why it cant make sure that a node not build or stabilize?
and we dont know the specifications of the knossos.
we doesnt know it, that i doesnt can lock node, we only know that it can stabilizes or create nodes.
any we dont know how the portal was, before the trinity "activate" it.
and the GTVA only guess the Trinity "activate" the portal (i mean here not that the Trinity wasnt there or doesnt fly through).
the only person who definitive know if the portal was inactiv or in a lock mode is Bosch, he was the only person who know how to use the portal and that behind the portal the shivan lurking.
and the lucifer: that fleet was the only contact in Ross 128, since 33 year have we there see no another shivan.
if bosch doesnt use the portal, maybe the next shivans came through in X years.
so i think, the ancients close/lock the portal, but the shivans search for another way and find it.
maybe the way over the natural nodes 100 or 1000 years long, but definite lager as 33 years.
the remians sathans: i believe the reason why they stay was only to stabilize the prozess in the sun long enough, that the other sathans can jump through the sun.
but this coast so much energy that the sathans energy-reserve go down respectively the sathans dies.
you see it, the sathans jump out, the remains go off and the sun exploded immediately after the lights go out.
i doesnt see any other reason why this sathans should stay.