SqlFileStream error after SQL Server 2016 (SP2-CU3) upgrade (the device is not ready

We've had this .NET component (.exe) running to migrate documents between 2 databases for almost a year. Console app is using the System.Data.SqlTypes.SqlFileStream .NET class to read/write from file system.

After a recent upgrade of SQL Server to SQL Server 2016 (SP2-CU3) (KB4458871) - 13.0.5216.0 (X64) - the console app has stopped working and throws the following error when trying to open specific document for read operation:

System.ComponentModel.Win32Exception (0x80004005): The device is not ready

We double-checked FILESTREAM properties on both databases to make sure they are enabled (just in case they were removed somehow during the upgrade) and we confirmed they are configured as needed.

We are running out of troubleshooting options as we don't know what to check for. All ports seem to be open between the app server where this tool runs and the database servers (same as before).

Let me know if anybody has any idea what could have changed after recent SQL Server upgrade.

just in case someone faces the same issue... we were able to resolve this by actually disabling FILESTREAM, rebooting servers, enabling FILESTREAM back on. Issue was related to some un-mapped path of physical drives for SQL (sorry i cant provide more details)