Hi,
the regular expression in line 71 deletes "./grub/grubenv" only partially on an EFI partition:
./efi/boot/grub/grubenv
->
./efi/boo
As a result, the checksum for efi/boo cannot be calculated, leading to an error message.
I assume a small fix is escaping the dot too:
files=echo $files | sed "s/\.\/grub\/grubenv//" # remove files that should be skipped
Kind regards
Holger