Error in Migration : MigrationProvisioningPermanentException: The proxy address is already in use

I am in the process to do cutover migration from Exchange 2013 to ExO. I had an error in a group of mailboxes, as a result, they have different primary addresses than the default ones and I had to permanently remove them from Office365 using powershell then I removed this migration batch and created another one. When all the mailboxes synced I had errors in these group of mailboxes but not all of them:

mailto:User1@company2.co.uk

Error: MigrationProvisioningPermanentException: The proxy address "smtp:mailto:user1@company1.co.uk" is already being used by the proxy addresses or LegacyExchangeDN of "user1 CNF:71f8a0d4-d2d7-4ff5-a5f0-bd76d84a5564". Please choose another proxy address. --> ( The "UserMailbox" with display name "user1" is already setup and using the same address.) --> The proxy address "smtp:mailto:user1@company1.co.uk" is already being used by the proxy addresses or LegacyExchangeDN of "user1 CNF:71f8a0d4-d2d7-4ff5-a5f0-bd76d84a5564". Please choose another proxy address. --> ( The "UserMailbox" with display name "user1" is already setup and using the same address.)

The default domain is https://company2.co.uk/ and https://company1.co.uk/ is an alias and accepted domain in O365.. I have a ticket with MS for three days now and no luck deleting the orphaned mailboxes.

I can see the orphaned mailboxes from the shell but I can't remove them as they will not recognised by any delete command either from remove-msoluser, remove-mailbox and

Set-User -PermanentlyClearPreviousMailboxInfo

Any bright idea is much appreciated.