Unable to complete backup over SFTP

SFTP の宛先を使用して php occ backup:point:create で失敗を再現し、次に lib/private/Files/Storage/Common.php:209 から開始して、trace に示されている storage wrapper のフレームを追ってください。SFTP 経由でバックアップが完了するように、失敗の原因を特定して解決できれば完了です。

NC 24.0.4
Backup app 113

Backup fails after writing some metadata to external storage.
Fails when the backup is configured to write over sftp

Any idea?

/home/user/cloud $ php occ backup:point:create
> maintenance mode: on
> initialization of the AppData
> initialization of the RestoringPoint: 20220905085730-full-cwsnFq9muHLAMoe based on NC24.0.4.1
> initialization of the storage
> preparation of the data to be stored in the restoring point
> preparation of internal data
> maintenance mode: off
An unhandled exception has been thrown:
TypeError: fwrite(): Argument #1 ($stream) must be of type resource, bool given in /home/user/cloud/lib/private/Files/Storage/Common.php:209
Stack trace:
#0 /home/user/cloud/lib/private/Files/Storage/Common.php(209): fwrite(false, '')
#1 /home/user/cloud/lib/private/Files/Storage/Wrapper/Wrapper.php(258): OC\Files\Storage\Common->file_put_contents('backup/20220905...', '')
#2 /home/user/cloud/lib/private/Files/Storage/Wrapper/PermissionsMask.php(112): OC\Files\Storage\Wrapper\Wrapper->file_put_contents('backup/20220905...', '')
#3 /home/user/cloud/lib/private/Files/Storage/Wrapper/Wrapper.php(258): OC\Files\Storage\Wrapper\PermissionsMask->file_put_contents('backup/20220905...', '')
#4 /home/user/cloud/lib/private/Files/Storage/Wrapper/Availability.php(274): OC\Files\Storage\Wrapper\Wrapper->file_put_contents('backup/20220905...', '')
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