Not sure if I've gotten the third shadowcrystal or not, help on finding what to do

(Apologies for posting here, not enough karma on r/Deltarune)

Originally, I didn't know about the shadow crystals being a thing in each chapter until I beat Spampton and went on to look up what shadowcrystals were do discover that Jevil has one too.

I went back to the end of my Chapter 1 save file and beat Jevil to get his shadowcrystal and returned to Chapter 2 to pick it up in the hole along with Jevil's other item drops.

When I first got to the knight in my first playthrough of Chapter 3, I of course, failed as I didn't see it coming and did not get the ShadowMantle. I continued on to Chapter 4, but just up to the first save point, after the church.

I had been using Slot 1 on the saves all the way from Chapter 1-4, until I went back and defeated the knight. I didnt get the Shadow Mantle as I hadn't gotten and S grade on the first round. Before I defeated the knight, I made a save on Slot 3 where I had went back and picked up a few items to help with the fight, notably emptying the gacha machine, where I also got the Tenna Trophy.

Going into Chapter 4 on all save slots shows that I do not have a third shadow crystal (Only [2] show in my key items), Seam makes no dialogue about dying to or beating the Knight (with or without Mantle), and no Tenna Trophy in Kris' room.

I'm not sure what to do to get the Knights Crystal onto the save with the other two crystals I've gotten so far. Another note is that I dont have a completion file for save slot 1, but I do for 2 and 3. Somewhere along the way I must have switched to save slot 2 and died to the Knight. Annoyingly, I entered the Church's Dark World before going to Castle Town.

In short, how can I get my Save Slot 1 Crystals (Chapter 1-2) to get onto my Save Slot 3?
Will I have to back and beat the Knight again on my Save Slot 1 to get the completion file to carry over?

Thanks for your time and help