diff --git a/TBF/BenchControl/Operations/CheckUIOp.cs b/TBF/BenchControl/Operations/CheckUIOp.cs
index ca4ad90b9..f651de58d 100644
--- a/TBF/BenchControl/Operations/CheckUIOp.cs
+++ b/TBF/BenchControl/Operations/CheckUIOp.cs
@@ -55,12 +55,12 @@ namespace TBF.BenchControl.Operations
 
         public Event Run()
         {
-            if (Bridge.Ui2MachineQueue.Count <= 0) return Event.None;
-
             UI2BenchCmd cmd;
 
             lock (Bridge.Ui2MachineQueue)
             {
+                if (Bridge.Ui2MachineQueue.Count <= 0) return Event.None;
+
                 if (Bridge.Ui2MachineQueue.Contains(UI2BenchCmd.Stop))
                 {
                     do {
@@ -68,6 +68,13 @@ namespace TBF.BenchControl.Operations
                     }
                     while (cmd != UI2BenchCmd.Stop);
                 }
+                else if (Bridge.Ui2MachineQueue.Contains(UI2BenchCmd.Shutdown))
+                {
+                    do {
+                        cmd = Bridge.Ui2MachineQueue.Dequeue();
+                    }
+                    while (cmd != UI2BenchCmd.Shutdown);
+                }
                 else
                 {
                     cmd = Bridge.Ui2MachineQueue.Dequeue();
diff --git a/TBF/BenchControl/Sequences/MainSeq.cs b/TBF/BenchControl/Sequences/MainSeq.cs
index ec3f7ec80..06affd381 100644
--- a/TBF/BenchControl/Sequences/MainSeq.cs
+++ b/TBF/BenchControl/Sequences/MainSeq.cs
@@ -1178,6 +1178,8 @@ namespace TBF.BenchControl.Sequences
         {
             log.WarnFormat("MakeSelection({0})", context);
 
+            IOperation checkUiOpWithClear = new Operations.CheckUIOp(true);
+
             bool shutdownInProgress = false;
 
             /// Tank emptying valves states
@@ -1222,7 +1224,7 @@ namespace TBF.BenchControl.Sequences
 
 
                 State.Create("MainSeq : Select an activity")
-                    .AddOperation(checkUiOp)
+                    .AddOperation(checkUiOpWithClear)
                     .AddOperation((StateMachine.Scale1 != null) ? StateMachine.Scale1.ReadMassOp(ref mass1) : null)
                     .AddOperation((StateMachine.Scale2 != null) ? StateMachine.Scale2.ReadMassOp(ref mass2) : null)
                     .AddOperation((StateMachine.Scale3 != null) ? StateMachine.Scale3.ReadMassOp(ref mass3) : null)
@@ -1237,6 +1239,7 @@ namespace TBF.BenchControl.Sequences
                     {
 #if true
                         /// TBF shutdown without tank draining
+                        log.Fatal("Returning from MakeSelection() after e.Contains(Event.UiCmdShutdown)==true");
                         return Selection.Shutdown;
 #else
                         /// TBF shutdown with tank draining
diff --git a/TBF/BenchControl/StateMachine.cs b/TBF/BenchControl/StateMachine.cs
index ad1b627c0..3a6fba111 100644
--- a/TBF/BenchControl/StateMachine.cs
+++ b/TBF/BenchControl/StateMachine.cs
@@ -625,7 +625,9 @@ namespace TBF.BenchControl
 
 			new Sequences.MainSeq().Execute(null);
 
+            log.Fatal("StateMachine.Worker() before State.StopOperations()");
             State.StopOperations();
+            log.Fatal("StateMachine.Worker() after State.StopOperations()");
 
             stateMachineRunning = false;
         }
diff --git a/TBF/MainWnd.cs b/TBF/MainWnd.cs
index 4ae98d02a..dbb16165a 100644
--- a/TBF/MainWnd.cs
+++ b/TBF/MainWnd.cs
@@ -576,12 +576,22 @@ namespace TBF
             {
                 if (BenchControl.StateMachine.Running)
                 {
-                    Bridge.Ui2Bench(UI2BenchCmd.Shutdown);          /// Drain tanks and quit the main sequence
+                    int elapsedTimeMs;
                     do
                     {
-                        Thread.Sleep(100);
+                        Bridge.Ui2Bench(UI2BenchCmd.Shutdown);  /// Quit the main sequence, optionally drain tanks
+                        elapsedTimeMs = 0;
+                        do
+                        {
+                            Thread.Sleep(100);
+                            elapsedTimeMs += 100;
+                        }
+                        while (BenchControl.StateMachine.Running && elapsedTimeMs < 3000);  /// Wait until StateMachine.Worker() completes
+
+                        if (elapsedTimeMs < 3000) break;
                     }
-                    while (BenchControl.StateMachine.Running);      /// Wait until StateMachine.Worker() completes
+                    while (elapsedTimeMs >= 3000);  /// Keep resending UI2BenchCmd.Shutdown on 3s timeouts (BenchControl.StateMachine.Running stays true for 3s)
+ 
 
                     /// Show 'Closing_Test_Bench_Framework' modeless window in separate thread
 				    var form = new TBF.Forms.ModelessActivityForm()
diff --git a/TBF/Properties/AssemblyInfo.cs b/TBF/Properties/AssemblyInfo.cs
index 3e890bbfa..29325d8a0 100644
--- a/TBF/Properties/AssemblyInfo.cs
+++ b/TBF/Properties/AssemblyInfo.cs
@@ -29,5 +29,5 @@ using System.Runtime.InteropServices;
 //      Build Number
 //      Revision
 //
-[assembly: AssemblyVersion("2.18.812.0")]
-[assembly: AssemblyFileVersion("2.18.812.0")]
+[assembly: AssemblyVersion("2.18.813.0")]
+[assembly: AssemblyFileVersion("2.18.813.0")]