Have you previously installed updates for these games via cia? If you have, it causes an issue where the updates will fail to download from the eShop.
If this is the issue, there's a somewhat complicated way to fix it. Make a backup of your emuNAND and all of the files on your SD card (alternatively, you can use a different SD card). Format a new emuNAND. Update your new emuNAND. Go to the eShop and download the updates for the games you were unable to update previously. It should download. After you've downloaded all of the updates that you were unable to, restore your emuNAND backup and your SD card backup. Go back to the eShop with your restored emuNAND and try to download the updates. It should now succeed.
I think I may have discovered the problem(s).
First one comes with Shovel Knight as I had the .cia version on 1.2. After that, Yatch Club Games released a mayor update and a retail version of the game. That update had to be applied by redownloading the whole game as I've read, so, redownloading something not purchased at eShop causes the error. Since I also have a Sky3DS+, I've decided to change to the .3ds version and I've succesfully updated the game to it's latest version.
Next is SSB, which may be caused due to a mistake I made; it was an USA .cia, instead of an EUR .cia, so the eShop wasn't able to provide me the update, causing the error. I'm updating it now and doesn't seem to cause any problem. I'll edit this post when it finish.
EDIT: I've succesfully downloaded the update
Finally, regarding Mario Kart, a friend told me that sometimes, the game asks you to update even though you might be on the latest version, so I'll check if it is that right after the Smash Bros update finishes.
EDIT: Update is still giving me some issues, so I'll try to download a new one and give it a try.
EDIT2: Still having issues, so I've decided to install one with the update already patched :3
Thanks for the reply anyways
