It may be related to a timer job that deletes subsites under the Arabic/English variation site after a period of inactivity.
However, it is also possible that there is another underlying issue causing this behavior. It is recommended that you review the SharePoint logs and event viewer to see if there are any errors or warnings related to the subsites being deleted.
Additionally, you may want to consider reaching out to Microsoft Phone Support for further assistance in troubleshooting this issue.
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