If you think it could be the DLC, try backing up the save with JKSV and delete everything (save data, DLC, updates). After updating it back, restore the save.
Okay I think I got this to work after a while. In the directories folder (don't rename it, don't capitalise anything), I removed the Items folder. Then use JKSV to restore the BCAT (NOT in applet mode), and restart the Switch immediately. And finally got to 1.1.1a with Zipper in the plaza.
You should have backup the save file. Anything now would probably be too late. You can try importing the old bcat though, after deleting the directories.
How do I know if this works? I imported the BCAT but nothing happened. Also, is it important to mention that in the first boots of JKSV, I keep getting this image of this weird guy instead of my games and profiles?
I supposed so, yeah.
Just to make sure, since you didn't directly reply to rokusnow04, you have been using an edited save for over half a year and not banned right? I mean, I was just gonna inject the save but then ACNH came out with an insta-ban code, so I kind of have second thoughts.