"not a valid root device" error in UEFI chainloader command

[Keshav P R]

Hi,
     I tried to manually chainload UEFI shell from grub2 terminal in
x86_64 firmware. I get

> insmod part_gpt
> insmod fat
> chainloader (hd0,gpt1)/shellx64.efi
error: not a valid root device

If I use

> set pager=1
> set debug=all
> chainloader (hd0,gpt1)/shellx64.efi
[long rows of text - but no visible error]
> boot
[shell launched]

However a menuentry like

menuentry "UEFI Shell" {
        search --fs-uuid --no-floppy --set=root ${_uefi_sys_fs_uuid}
        chainloader (${root})/shellx64.efi
}

works. I can reproduce this error everytime I try to manually
chainload from grub2 terminal, but does not occur even once when
loaded via menuentry. Thanks in advance.

Regards.

Keshav