(SPOILERS) Help with getting Ending 3 in Cosmic Forge

Hey there, posted a few weeks ago asking for some hints in the castle 50 hours later I’m now basically done, I’m in the chamber of the cosmic forge. The problem is I don’t want to take it, I’ve killed Rebecca and the King so I don’t have the key needed. I don’t have anyone really trained in lockpicking, my bard has a few points but I realized the skill was “useless” when my bard and mage can just use knock-knock on anything locked and have it work just as well. But knock knock doesn’t seem to be working, using reloads I’ve tried 50+ times and the door to the chamber with the ship isn’t opening. I’ve looked up a guide and it says it can be opened with knock knock but is this actually true? I’m using it at max power