@Gaak78 I'm @ing you here because I can't respond to a review.
As a modder, I am very much convinced that you do have M4-78 installed and you just don't know it. Unless Leilukin can prove otherwise, those journal entries aren't left over content regarding M4-78, rather, those are journal entries added by the M4-78EP mod. I imagine you unknowingly installed M4-78EP and installed this mod on top thus causing a conflict, or you have M4-78EP subscribed on the Steam Workshop unknowingly and this is how you're getting this bug.
Again, Leilukin could swoop in and prove me wrong or you can check for yourself and prove me wrong again - but this is what you're bug seems like to me.
I think the idea is that the area Vash is in is on the other side of Ludo Kresh's tomb area. In Kreia's dialogue, she says there is a "chamber" beyond that tomb area which can lead the player out - that is where Vash is being held in this mod.
Though you are correct, the "chamber" is quite literally a reuse of the very front of the tomb.
That could work, it doesn't even need to be AI I think a spliced or a reused dialogue could do what you want. Though that would be up for Leilukin to decide.