Wiikey's are picky, that said, I've only ever dealt with two, the one in my SLGC(which is a Sega) and the one Ashen wired to my XGC, which is more or less, the wiikey fusion of Jesus in comparison.
The one on the XGC loads every single time. I never get header errors or WBFS errors.
However, on the SLGC? I've found myself restarting the cube 10-15 times before I even get it to display the games on the menu. I mean, with the switch fix, I always get the GClinux image to pop up in the bios, but getting the menu afterwards to show the games from the SD card, it's ridiculous.
SS