Duplicate mailboxes

We discovered few users having mailboxes on both ONprem (2010) and Online. Get-mailbox, get-recipient, stats work on both the onprem & online. get-recipient shows user mailbox even the EMC search shows user mailbox.
MSOLuser gives account inf and licenses assigned.
From get-mailboxstat -include move history we have logs that these mailboxes are moved to online. The onprem mailbox stat shows very few or no emails.
Users are having issues with autodiscover. Please advise with the resolution steps for this use case.
o365AdmAsked:
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Vasil Michev (MVP)Commented:
Ditch the on-prem one, as you have already (planned to) moved it, by converting it to mail-enabled user. You can export the messages and send the pst to the user.

If you can repro this or have detailed steps to describe what happened, open a ticket with Microsoft as they were looking for examples of such behavior (well looking to confirm it, as it seems people run into this situation occasionally but no one seems to be able to reproduce this reliably yet).

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o365AdmAuthor Commented:
Thank you again Vasil.
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