I contacted Microsoft support. They agree that it does have to do with Oracle12c upgrade and provided workaround for the issue.

FROM DAC Connection:

Workaround to add oracle publisher support w/o new datatype support:

exec sys.sp_MSrepl_ORAdatatypes 'Oracle', '12'

exec sys.sp_MSrepl_ORA_MSSQL_datatypemappings @source_dbms = N'ORACLE', @source_version = '12', @destination_dbms = N'MSSQLServer'

Warkaround to add oracle subscriber support w/o new datatype support:

exec sys.sp_MSrepl_ORAdatatypes 'Oracle', '12'

exec sys.sp_MSrepl_MSSQL_ORA_datatypemappings @source_dbms = N'MSSQLSERVER', @destination_dbms = N'ORACLE', @destination_version = '12'

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This worked for me and hopefully will help somebody else too!

Thanks!