"Unable to open the database file" UI Exception - 6.1

Upgraded UI and all servers on previous day to 6.1 release then closed out.

Opened UI and created a restore script - copy-pasted to SSMS and executed in a custom script. While the restore is executing, returned to UI and expanded 2 Server Groups but upon opening the second one each time (tried it opening the first then second listed, then second listed followed by first) and irrespective of the sequence of "expand"s, the UI Exceptions with the following and closes down:

SQLBackup

Unable to open the database file
unable to open database file
WorkerExecutionException

   at RedGate.SQLBackup.Engine.ConfigurableThreadPool.a(Exception )
   at RedGate.SQLBackup.Engine.ConfigurableThreadPool.a.b()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

----------

SQLiteException

Unable to open the database file
unable to open database file

   at System.Data.SQLite.SQLite3.Reset(SQLiteStatement stmt)
   at System.Data.SQLite.SQLite3.Step(SQLiteStatement stmt)
   at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery()
   at g.g(Server )
   at g.b(Object )