Extroot Pivot to External USB Overlay Not Triggering on GL-BE3600

Hello Support Team,

I am experiencing issues with configuring my GL-BE3600 router to use an external USB drive as its overlay (extroot). Despite following the recommended configuration steps, the router continues to mount the internal UBIFS overlay rather than pivoting to the USB drive.

Details of the Issue:

I have formatted my USB drive as ext4 with unsupported features disabled (using:
mkfs.ext4 -O ^64bit,^metadata_csum /dev/sda1).

My /etc/config/fstab is configured as follows:
   config global
        option delay_root '10'
        option auto_mount '1'
        option auto_swap '1'

    config mount
        option enabled '1'
        option uuid '83cb5d6a-b63e-47f5-8a6e-4b57acacff9d'
        option target '/overlay'
        option fstype 'ext4'
I've verified that the USB drive is recognized with the correct UUID (as confirmed via blkid /dev/sda1).

However, after rebooting, the output from df -h still indicates:
`/dev/ubi0_3 on /overlay (internal UBIFS overlay)`

    The union mount (overlayfs:/overlay on /) is limited to 355.6MB rather than reflecting the full capacity of the USB drive.

The dmesg logs show:
    "mount_root: loading kmods from internal overlay"
    "mount_root: switching to ubifs overlay"
I have also confirmed through logread that the system is processing /etc/config/fstab, and I manually triggered the block-mount process with /etc/init.d/fstab restart without any change.

I attempted to modify boot scripts (e.g., commenting out potential calls to remount_ubifs in /etc/rc.local) to prevent the internal overlay from re-mounting, but the pivot still does not occur.

Summary:
Despite the correct configuration and attempts to increase the USB initialization delay, the extroot pivot is not being triggered. The router continues to boot using its internal overlay, which limits the available writable space to about 355.6MB instead of utilizing the full capacity of the external USB drive (approximately 7GB).

Could you please help me diagnose and resolve this issue so that the router successfully pivots to the external USB overlay?

Thank you for your assistance.