Thanks @mikaelmello! That was where I needed to look. Here is the latest log from “About --> Show Logs”
**Dec 10, 2018 12:13 AM: Failed while executing "Backup" with id: 1**
>System.NullReferenceException: Object reference not set to an instance of an object
> at Duplicati.Library.Utility.FileBackedList`1[T].Add (Duplicati.Library.Utility.T value) <0x41ee3230 + 0x002a2> in <filename unknown>:0
> at Duplicati.Server.WebServer.RESTMethods.CommandLine+LogWriter.WriteLine (System.String value) <0x41f3d0b0 + 0x00123> in <filename unknown>:0
> at System.IO.TextWriter.WriteLine (System.String format, System.Object arg0, System.Object arg1) <0x7f23a37d4f10 + 0x0009b> in <filename unknown>:0
> at Duplicati.CommandLine.ConsoleOutput.WriteMessage (Duplicati.Library.Logging.LogEntry entry) <0x41f4a7d0 + 0x000d4> in <filename unknown>:0
> at Duplicati.Library.Main.MultiMessageSink.WriteMessage (Duplicati.Library.Logging.LogEntry entry) <0x41f4a750 + 0x0004e> in <filename unknown>:0
> at Duplicati.Library.Main.ControllerMultiLogTarget.WriteMessage (Duplicati.Library.Logging.LogEntry entry) <0x41ee2bc0 + 0x000c7> in <filename unknown>:0
> at Duplicati.Library.Logging.LogScope.WriteMessage (Duplicati.Library.Logging.LogEntry entry) <0x41dac5c0 + 0x00058> in <filename unknown>:0
> at Duplicati.Library.Logging.Log.WriteMessage (LogMessageType type, System.String tag, System.String id, System.Exception ex, System.String message, System.Object[] arguments) <0x41dabf90 + 0x000c7> in <filename unknown>:0
> at Duplicati.Library.Logging.Log.WriteErrorMessage (System.String tag, System.String id, System.Exception ex, System.String message, System.Object[] arguments) <0x41f27380 + 0x0003f> in <filename unknown>:0
> at Duplicati.Library.Main.Controller.RunAction[T] (Duplicati.Library.Main.T result, System.String[]& paths, IFilter& filter, System.Action`1 method) <0x41ed6030 + 0x00b3b> in <filename unknown>:0
> at Duplicati.Library.Main.Controller.Backup (System.String[] inputsources, IFilter filter) <0x41ed43b0 + 0x002eb> in <filename unknown>:0
> at Duplicati.Server.Runner.Run (IRunnerData data, Boolean fromQueue) <0x41ec4680 + 0x010a3> in <filename unknown>:0