Database connection lost after editing screen

I have added a database connection in Advanced Customisation / Tables and Databases.  I'm able to retrieve data successfully using the usual CRM objects.  However, if I edit a CRM screen layout and save it, the database connection disappears until I run a metadata refresh for Tables and Columns.  The self service database also disappears and reappears after the metadata refresh.  This is on CRM 2021 R1.

Is this a known issue?