diff --git a/misc/version.txt b/misc/version.txt
index cb36e65..b6a8162 100644
--- a/misc/version.txt
+++ b/misc/version.txt
@@ -1 +1 @@
-1.2.1.0
\ No newline at end of file
+1.2.1.1
\ No newline at end of file
diff --git a/src/BreCalClient/BreCalClient.csproj b/src/BreCalClient/BreCalClient.csproj
index dd0f203..9e5c884 100644
--- a/src/BreCalClient/BreCalClient.csproj
+++ b/src/BreCalClient/BreCalClient.csproj
@@ -8,8 +8,8 @@
     <SignAssembly>True</SignAssembly>
     <StartupObject>BreCalClient.App</StartupObject>
     <AssemblyOriginatorKeyFile>..\..\misc\brecal.snk</AssemblyOriginatorKeyFile>
-    <AssemblyVersion>1.2.1.0</AssemblyVersion>
-    <FileVersion>1.2.1.0</FileVersion>
+    <AssemblyVersion>1.2.1.1</AssemblyVersion>
+    <FileVersion>1.2.1.1</FileVersion>
     <Title>Bremen calling client</Title>
     <Description>A Windows WPF client for the Bremen calling API.</Description>
     <ApplicationIcon>containership.ico</ApplicationIcon>
diff --git a/src/BreCalClient/MainWindow.xaml.cs b/src/BreCalClient/MainWindow.xaml.cs
index 2494f64..8e40e2d 100644
--- a/src/BreCalClient/MainWindow.xaml.cs
+++ b/src/BreCalClient/MainWindow.xaml.cs
@@ -38,7 +38,8 @@ namespace BreCalClient
 
         #region Fields
 
-        private static int _uiUpdateRunning = 0;
+        //private static int _uiUpdateRunning = 0;
+        private static SemaphoreSlim uiLock = new SemaphoreSlim(1);
         
         private Credentials? _credentials;
 
@@ -237,7 +238,7 @@ namespace BreCalClient
             NewWithModel(null);
         }
 
-        private void NewWithModel(ShipcallControlModel? model)
+        private async void NewWithModel(ShipcallControlModel? model)
         {
             EditShipcallControl esc = new()
             {
@@ -252,7 +253,9 @@ namespace BreCalClient
                 // create UI & save new dialog model
                 if (esc.ShipcallModel.Shipcall != null)
                 {
+                    await uiLock.WaitAsync();
                     this.UpdateUI();
+                    uiLock.Release();
 
                     esc.ShipcallModel.Shipcall?.Participants.Clear();
                     foreach (ParticipantAssignment pa in esc.ShipcallModel.AssignedParticipants.Values)
@@ -346,10 +349,12 @@ namespace BreCalClient
             this.FilterShipcalls();
         }
 
-        private void SearchFilterControl_SearchFilterChanged()
+        private async void SearchFilterControl_SearchFilterChanged()
         {
             this.FilterShipcalls();
+            await uiLock.WaitAsync();
             this.UpdateUI();
+            uiLock.Release();
         }
 
         private void checkboxShowCancelledCalls_Checked(object sender, RoutedEventArgs e)
@@ -358,11 +363,13 @@ namespace BreCalClient
             this.SearchFilterControl_SearchFilterChanged();
         }
 
-        private void comboBoxSortOrder_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
+        private async void comboBoxSortOrder_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
         {
             _sortOrder = (Extensions.SortOrder) this.comboBoxSortOrder.SelectedIndex;
             this.FilterShipcalls();
+            await uiLock.WaitAsync();
             this.UpdateUI();
+            uiLock.Release();
         }
 
         private void buttonHistory_Click(object sender, RoutedEventArgs e)
@@ -502,15 +509,18 @@ namespace BreCalClient
                     }
 
                     this.FilterShipcalls();
-                    this.UpdateUI();                    
+                    await uiLock.WaitAsync();
+                    this.UpdateUI();
+                    uiLock.Release();
                 }
 
                 try
                 {
                     double interval = (double) SHIPCALL_UPDATE_INTERVAL_SECONDS / PROGRESS_STEPS;
 
-                    if (Interlocked.CompareExchange(ref _uiUpdateRunning, 1, 0) == 1) // do not restart progress unless UI update has completed
-                        await Task.Delay(TimeSpan.FromSeconds(interval));
+                    
+                    //if (Interlocked.CompareExchange(ref _uiUpdateRunning, 1, 0) == 1) // do not restart progress unless UI update has completed
+                    //    await Task.Delay(TimeSpan.FromSeconds(interval));
 
                     System.Diagnostics.Trace.WriteLine("restarting refresh countdown");
                     for (int i = 0; i < PROGRESS_STEPS; i++)
@@ -770,7 +780,7 @@ namespace BreCalClient
 
             this.Dispatcher.Invoke(new Action(() =>
             {
-                if (Interlocked.CompareExchange(ref _uiUpdateRunning, 1, 0) == 1) return;
+                //if (Interlocked.CompareExchange(ref _uiUpdateRunning, 1, 0) == 1) return;
 
                 try
                 {
@@ -790,7 +800,7 @@ namespace BreCalClient
                 }
                 finally
                 {
-                    _uiUpdateRunning = 0;
+                   // _uiUpdateRunning = 0;
                 }
 
                 Mouse.OverrideCursor = null;
diff --git a/src/BreCalClient/Properties/PublishProfiles/ClickOnceProfile.pubxml b/src/BreCalClient/Properties/PublishProfiles/ClickOnceProfile.pubxml
index 8091412..c8a52ab 100644
--- a/src/BreCalClient/Properties/PublishProfiles/ClickOnceProfile.pubxml
+++ b/src/BreCalClient/Properties/PublishProfiles/ClickOnceProfile.pubxml
@@ -5,7 +5,7 @@ https://go.microsoft.com/fwlink/?LinkID=208121.
 <Project>
   <PropertyGroup>
     <ApplicationRevision>10</ApplicationRevision>
-    <ApplicationVersion>1.2.1.0</ApplicationVersion>
+    <ApplicationVersion>1.2.1.1</ApplicationVersion>
     <BootstrapperEnabled>False</BootstrapperEnabled>
     <Configuration>Release</Configuration>
     <CreateWebPageOnPublish>True</CreateWebPageOnPublish>