Grub cannot boot Windows: "error: not a valid root device"

Problem. I'm trying to setup a dual-boot Ubuntu/Windows installation. This has so far only succeeded partially: grub seems to detect my Windows installation, but cannot boot into it. When I select it, it provides a message saying 'error: not a valid root device."

Disks. I've constructed the dual-boot installation on two disks:

• /dev/sda contains Windows 10, UEFI. This OS was installed first, on one of the two drives. To prevent contamination, I had the other drive removed during installation. The drive contains four partitions:
  1. /dev/sda1, EFI system partition, FAT32, 100MB
  2. /dev/sda2, Microsoft reserved partition, unknown, 16MB
  3. /dev/sda3, Basic data partition, NTFS, 237+GB
  4. /dev/sda4, >>unnamed partition<<, NTFS, 530MB
• /dev/nvme0n1, the second drive, contains Ubuntu 22.04.1, UEFI. This OS was installed second. During installation, I opted for the "install along-side Windows" option. The drive contains two partitions:
  1. /dev/nvme0n1p1, EFI System partition, FAT32, 512 MB
  2. /dev/nvme0n1p2, >>unnamed partition<<, EXT4, 890+ GB

After installation. Following the installation, grub immediately recognized the Windows install, however, it returns "error: not a valid root device" each time I attempt to select it. I have executed sudo os-prober and sudo update-grub, both to no avail. The grub boot sequence is as follows:

insmod fat
set root='hd0,gpt1'
if [ x$feature_platform_search_hint = xy ]; then
  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  64DE-E837
else
  search --no-floppy --fs-uuid --set=root 64DE-E837
fi
chainloader /efi/Microsoft/Boot/bootmgfw.efi

Peculiarity. There is one thing that happens that I think is rather odd. Let's discuss three situations:

• When I turn my pc on, wait for grub to appear and select Windows, the error occurs.
• When I turn my pc on, enter the boot menu and select 'UEFI - Windows Boot Manager', I do boot into Windows.
• When I turn my pc on, enter the boot menu, select 'UEFI - Ubuntu' and then select Windows in grub, it also boots to Windows.

I'm baffled by the whole situation. Any input is much appreciated!