So, I have reattempted this and ran into the same issue with the technology researched.
I am doing it against all aggressive nightmare AIs but was able to knock one about by rushing them from there I managed to start rushing down a second ai and striped a bunch of worlds giving me enough resources to build up enough fleet and get mobile rulership on the wanderer.
Still unsure what's causing the bug, is it that the wander has a mobile fleet beacon?!
I'm still not even sure why I'm getting that specific error.
I've verified files and it did find one missing but I'm still getting the error when the titan tries to spawn.