Back up doesn't start

apps/backup/lib/Cron/Backup.php から始め、特に runDifferentialBackup の 126 行目を確認し、スケジュールされたジョブがその箇所に到達するまでの流れを調べてください。外部ストレージを使用し、Yunohost 上の Nextcloud 24.0.5 と Ubuntu 上の Nextcloud 24.0.2 で失敗を再現してください。バックアップジョブがこの記録されたエラーなしに開始して完了すれば完了です。

I have followed the documentation on how to set up back up, but it doesn't start.
I am using Nextcloud 24.0.5 via Yunohost and trying to make a back up and send it to external storage, Nextcloud 24.0.2 on Ubuntu.

This is the error from the log:
{"reqId":"RlUrBqqTpTjOQxbbrja4","level":3,"time":"2022-10-18T08:00:04+00:00","remoteAddr":"","user":"--","app":"backup","method":"","url":"--","message":"error while running differential backup - [{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":126,\"function\":\"runDifferentialBackup\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[]},{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":115,\"function\":\"runBackup\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[1666080004]},{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":97,\"function\":\"manage\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[]},{\"file\":\"\\/var\\/www\\/nextcloud\\/lib\\/private\\/BackgroundJob\\/Job.php\",\"line\":54,\"function\":\"run\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[null]},{\"file\":\"\\/var\\/www\\/nextcloud\\/lib\\/private\\/BackgroundJob\\/TimedJob.php\",\"line\":60,\"function\":\"execute\",\"class\":\"OC\\\\BackgroundJob\\\\Job\",\"object\":{},\"type\":\"->\",\"args\":[{},{}]},{\"file\":\"\\/var\\/www\\/nextcloud\\/cron.php\",\"line\":151,\"function\":\"execute\",\"class\":\"OC\\\\BackgroundJob\\\\TimedJob\",\"object\":{},\"type\":\"->\",\"args\":[{},{}]}]","userAgent":"--","version":"24.0.5.1","data":{"app":"backup"},"id":"634e7dce465c6"}