Investigating and fixing the cause of automatic backup failure of the "All-in-One WP Migration" plugin for WordPress sites

Question

　Server: conoha wing Premium plan 　WordPress: 6.4.1

Regarding the automatic backup function of the WordPress site plugin "All-in-One WP Migration", the backup is not completed and no e-mail regarding success or failure is received.

A blog site running on WordPress uses the plugin “All-in-One WP Migration” and the extension function of this plugin, “All-in-One WP Migration Google Drive Extension.” We create a backup of all site files and DB on Google Drive at a specified time every day. This began to fail several times a month from around May 2023, and the frequency of failures gradually increased after that, until around October 2023, no backups were generated at all. The email I set up to be sent upon success or failure has not yet arrived. After that, I changed the backup start time and the backup no longer failed, but the problem is that I can't specify it because it will fail with the original time, and there is still a possibility that it will happen again.

The following has been confirmed.

1. An email is sent when the backup is successful, but no email is sent when the backup fails
2. If the backup start time is 3:00 am, it will fail, but if it is 11:00 pm, it will succeed (it has been successful for about 2 or 3 weeks since December 2023)
3. According to an investigation using wp crontrol, there were no conflicts with events from other plugins.
4. Investigation by log output from the plugin file on the test server
   1. The plug-in starts normally at the specified time
   2. Loop the automatic backup process by re-registering the action in admin-ajax.php with a request using the wp_remote_request function from all-in-one-wp-migration/lib/controller/class-ai1wm-export-controller.php However, because the wp_remote_request request does not reach admin-ajax.php (admin-ajax.php is not loaded), the action is not registered and ends naturally, causing automatic backup to fail. It seems that the pattern is almost all (wp_remote_request is used for asynchronous communication, so the response cannot be confirmed and there is no sufficient supporting information)
5. On the test server, 503 errors sometimes occur, but the cause is unknown. This does not appear in conoha's error log, and no abnormality is observed in the resource log either when backup fails or when 503 occurs. Pleaseread the above and understand the situation to a certain extent before suggesting some kind of policy. I hope to be able to consult with you. (Please note that we will continue to update plugins in the future, so we generally recommend that you avoid changing the plugin file itself.) Although I am using a paid extension for all-in-one wp migration using google drive, the export function defined in all-in-one wp migration itself is used for automatic export, and there is a problem. There is a high possibility that this is occurring, so you can check it in your personal environment to some extent without purchasing the extension.

Several people have worked to investigate this error, but the issue has not been resolved.