Hero of Gavel Ending

Hey, new here. This post contains spoilers for the "Hero of Gavel" quest, so if you haven't done it yet, might wanna skip this one.

I put the text in white because I don't know how to blur. Highlight it to see what it says I guess.
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So, on my first playthrough of Hero of Gavel I killed Siegfried because I didn't know what I was doing. No issue, I like that there are multiple options. During that playthrough, I ran into a few issues concerning where Siegfried's walking NPC was located, but it all ended up fine.

Next playthrough, I decided I was gonna keep Siegfried alive and get the exclusive item for the good ending. I picked up the rope, the soft slime, and the pickaxe, but the problems were much worse this time. First, I made sure the items were real because I moved them from my hotbar to my regular inventory and they did not disappear. Next, when I right clicked the boulder to open the gate, my pickaxe disappeared and the boulder did nothing. Right click again, still nothing. No problem, it's not that big of a deal.

However, next is where it gets a little not fun. I got the rope from the airship, slime from the cave, both real items. Quest goes smooth until the final ascent bit - I right click to craft stuff at the tailor's machine, and my soft slime disappears. I get nothing, so I get the other items again and instead of getting soft boots, I got hard boots. Next, when I click to craft the parachute, my rope disappears and I don't get anything. I now don't have the soft slime or the rope, which means Siegfried will die and I don't get the good ending item.

All of this leads me to my question - can I get the good ending item (fandom says it's called Siegfried Agent's Key") in any other way? Like, can an admin or something give it to me or can I get the rope and soft slime again somehow? Or do I have to play another profile all the way to level 99 to try again?
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I think I'd be less bothered if this quest was earlier, because then I could quickly level a profile and get what I need again, but because it's so far in the end-game it would take a dozen or so hours to get back, and I don't want to spend that kind of time on this.