I am trying to use the Define Projection tool and a feature class in an enterprise geodatabase. I am receiving an error that it can't create a projection file (ERROR 000054). I have confirmed there is no locks on the table, the user logged in is the owner of the table and has db owner on the database. I am using a standard license. I've tried in both Pro and ArcCatalog (10.5.1). I've tried several tables with the same result. Is there security I am missing? Can there not be any locks on any table/view in the database while running the tool?
From the screenshot, the FC appears to be a stand-alone FC in the root level and not a FC in a feature dataset participating in a special relationship, like geometric network, topology, etc... Correct?
Check the database logs. If it is an issue on the DBMS that is forcing the error on the client, the logs should help you find the issue.