I´m having the same issue.
I use a silicon power micro SD card with fat32 format.
My system version is 5.5.1 U.
I have tried with the latest build of loadiine and with the stable version (0.2).
I have downloaded 4 versions of mario kart 8 and I have the same problem with each of them with no updates and tried to load the game with SSB and Mii Maker.
My other games load perfectly (TLOZ:TP, YWW, pokken tournament, star fox)
Edit: I didn´t find the rules so if I'm doing something wrong by posting the link just tell me and I will take it off.
Thanks.