Description of problem:

01_fallback_counting is run as a shell script and does not install any snippet into grub.cfg.

I suppose the file should be looking like this, that is "cat << EOF" added.

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#! /bin/sh -e

# Boot Counting
cat << EOF
if [ "\${boot_counter}" -a "\${boot_success}" = "0" ]; then
  if  [ "\${boot_counter}" = "0" -o "\${boot_counter}" = "-1" ]; then
    set default=1
    set boot_counter=-1
  else
    set boot_counter=$((\${boot_counter}-1))
  fi
  save_env boot_counter
fi
EOF
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