Ok, one update here: I was actually moving my configs from a Sandisk usb stick to a new Samsung one (that one recommeded on the forum). After doing that, both usb sticks stopped working. But I DID chage something: I renamed the drive name from "UNRAID" to "UNRAID-Y" and "UNRAID-S" so I could set the drives apart on my Mac... And that broke the boot. Renaming them again to the original "UNRAID" name, got everything back to work.