After you override the core in the Xi Cauldron (which unlike the others I’ve played through so far, happens pretty early), Aloy says “now I can override more machines”. But annoyingly, you don’t actually get the override until you finish the quest, which happens when you exit the cauldron. Along the way back you’ll encounter a few of the machines that require the Xi override and I found it frustrating when it wasn’t working. I was even thinking maybe it was a bug and I didn’t trigger something correctly, especially because Aloy mutters to herself, “I can’t override this machine yet—I’ll have to explore more cauldrons”. The game acts like you have the override, but you don’t get it until later. I googled but didn’t find anything, so I wrote this. If this happens to you, don’t be confused.