'Few cases are not getting created in Email-To-Case(With attachment)

I sent an email with an attachment from my mail(outlook and Gmail) account to the email address which is routed in my org and the case(with attachment) got created in salesforce org.

Here the issue is, it is working good sometimes and not working sometimes. I sent an email from multiple personal email IDs and I am facing the same issue. How to fix or debug this?



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