Managed Instance intermittently logs me in as DBO

Intermittently Azure Managed Instance logs me in as dbo when I log in using Entra. I will wake up the next day to find the problem gone.

This is an issue because when i try to create a new transactional replication publication

I get 

Msg 15007, Level 16, State 1, Procedure sys.sp_grant_publication_access, Line 112 [Batch Start Line 17]
'dbo' is not a valid login or you do not have permission.

Can anyone help me understand why Managed Instance sometimes logs me in as 'dbo' or should I raise a ticket..?

FYI - I am in the Entra Admin group on the server