Idea:  When the Scryve joined the Eight, the group was distrustful of their new member.   The star map they gave the Scryve was missing a few stars, stars that are visible in the Precusor stargate Hypergate map but absent from the map the Scryve are using.   This is the same star map they supplied the Tywon and that Star Control is relying on.

The Scryve never noticed as they cannot access the starbases left by the Precursors and they don't manually navigate in Hyperspace like "savages".   

There are two ways to find these worlds, one is to navigate manually in hyperspace and head towards them and the other is to study and compare the map in the starbases versus those in programmed in our ship.

The remnants of the Eight can be found in those star systems.