uninstalled both OnGuard and SQL server. rebooted machine. no firewall / no anti-virus.
did the sqllocaldb trick, ran OnGuard as administrator just for giggles.
no obvious errors with OnGuard during start up. Same SQL errors in log. However, I think I fixed it with blunt force
error example below:
2020.12.25 19:16:15:3218 - MainWindow - InsertMotionIfNecessary - Sql Exception on opening database connection: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 56 - Unable to load the SQLUserInstance.dll from the location specified in the registry. Verify that the Local Database Runtime feature of SQL Server Express is properly installed.)
2020.12.25 19:17:05:3310 - MainWindow - InsertMotionIfNecessary - Sql Exception on opening database connection: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 56 - Unable to load the SQLUserInstance.dll from the location specified in the registry. Verify that the Local Database Runtime feature of SQL Server Express is properly installed.)
2020.12.25 19:18:39:2416 - MainWindow - InsertMotionIfNecessary - Sql Exception on opening database connection: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 56 - Unable to load the SQLUserInstance.dll from the location specified in the registry. Verify that the Local Database Runtime feature of SQL Server Express is properly installed.)
2020.12.25 19:37:52:6691 - On Guard started at: 12/25/2020 7:37:52 PM
2020.12.25 19:40:38:0765 - 0 interesting objects found in file: D:\AI\AI_Front.20201225_194037565.jpg
Just a complete wall of those SQL errors in no discernable time line pattern while idle (no events at those times).
How I fixed it (at least, no SQL errors as of yet since 10:30pm last night)... I downloaded/installed the 2019 SQL Lite Express from Microsoft, thinking I needed the SQL Server Configuration Manager itself to start indepth troubleshooting (I think this is the only way to see the associated network port, related names, etc).
So...let's chalk up the errors I've been having to my unique personal PC & Windows. Maybe goofy initial Windows installation or something else.