Please check all the other HDDs or SSDs for an EFI partition.
make sure that one of the drives with the EFI partition contains the missing EFI folder and the default.plist.
is your OSX HDD connected to the first SATA Port?
I checked all my drives, and none of them contains Defaults.plist:
My boot drive is connected to port0, I believe (the top one on the motherboard, and BSD name is disk0).
@neoyoli
Try to use "EFI Mounter" to mount the EFI
bevor using Multibeast
I tried it, same thing...