First off, this issue happened on 0.10.2, 0.10.5 and 0.11.x for me so far.
i used any information i could get: forums, wiki, some other boards. they all stated that you need 3 legendary items in the research station, 1 of which can or has to be another XSTN-K artifact.
my first try was with 2 artifacts, thats when i realized you may only have 1. my 2nd try was with 1 artifact and 1 legendary turret and 1 legendary upgrade. again it failed for some reason and i got a turret.
ofc this continued when i tried it again with 2 legendary turrets and an artifact.
just to try, i even used 4 legendary items together with 1 artifact, just to get another legendary turret out of it.
my last try was 2 turrets and 1 upgrade. sadly i, once again, got a turret out of it. there has been no sight of the XSTN-K II artifact during my whole playtime.
the one thing i didnt try yet was 3 legendary upgrades. but i fear it will have the same result. i will try the upgrade one in a bit when i actually get the stuff for it.
in case even that fails, does anyone have an idea as for why im simply unable to get that artifact? i mean in a way its sort of game breaking, as it keeps me from passing the barrier, thus getting ogonite and avorion or reaching the center.
thanks in advance. also i didnt see the need to provide any logs. in case im mistaken and you still want the logs, i will upload them right away.