diff --git a/src/BreCalClient/MainWindow.xaml.cs b/src/BreCalClient/MainWindow.xaml.cs
index 1a01de8..2385ce6 100644
--- a/src/BreCalClient/MainWindow.xaml.cs
+++ b/src/BreCalClient/MainWindow.xaml.cs
@@ -38,8 +38,9 @@ namespace BreCalClient
 
         #region Fields
 
-        private static Int32 _uiUpdateRunning = 0;
-        
+        //private static int _uiUpdateRunning = 0;
+        private static SemaphoreSlim uiLock = new SemaphoreSlim(1);
+
         private Credentials? _credentials;
 
         private readonly ConcurrentDictionary<int, ShipcallControlModel> _allShipcallsDict = new();
@@ -50,7 +51,7 @@ namespace BreCalClient
         private readonly UserApi _userApi;
         private readonly TimesApi _timesApi;
         private readonly StaticApi _staticApi;
-        private readonly ShipApi _shipApi;        
+        private readonly ShipApi _shipApi;
 
         private CancellationTokenSource _tokenSource = new();
         private LoginResult? _loginResult;
@@ -91,16 +92,16 @@ namespace BreCalClient
             _staticApi = new StaticApi(Properties.Settings.Default.API_URL);
             _staticApi.Configuration.ApiKeyPrefix["Authorization"] = "Bearer";
             _shipApi = new ShipApi(Properties.Settings.Default.API_URL);
-            _shipApi.Configuration.ApiKeyPrefix["Authorization"] = "Bearer";            
+            _shipApi.Configuration.ApiKeyPrefix["Authorization"] = "Bearer";
 
             const int maxDelayInMilliseconds = 32 * 1000;
             var jitterer = new Random();
 
-            var retryPolicy = 
+            var retryPolicy =
             //    Policy.Handle<HttpRequestException>()
                 Policy.HandleResult<RestSharp.RestResponse>(resp => resp.StatusCode == HttpStatusCode.Unauthorized)
                 //.OrResult<RestSharp.RestResponse>
-                .WaitAndRetryAsync(1, 
+                .WaitAndRetryAsync(1,
                 retryAttempt =>
                 {
                     var calculatedDelayInMilliseconds = Math.Pow(2, retryAttempt) * 1000;
@@ -171,7 +172,7 @@ namespace BreCalClient
                         this._staticApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
                         this._shipApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
                         this.LoadStaticLists();
-                        this.labelUsername.Text = $"{_loginResult.FirstName} {_loginResult.LastName}";                        
+                        this.labelUsername.Text = $"{_loginResult.FirstName} {_loginResult.LastName}";
                     }
                 }
                 labelGeneralStatus.Text = $"Connection {ConnectionStatus.SUCCESSFUL}";
@@ -211,9 +212,9 @@ namespace BreCalClient
                         this._timesApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
                         this._shipcallApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
                         this._staticApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
-                        this._shipApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;                        
+                        this._shipApi.Configuration.ApiKey["Authorization"] = _loginResult.Token;
                         result = true;
-                    }                    
+                    }
                 }
                 else
                 {
@@ -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)
@@ -445,7 +452,7 @@ namespace BreCalClient
 
                     this.Dispatcher.Invoke(new Action(() =>
                     {
-                        labelGeneralStatus.Text = $"Connection {ConnectionStatus.SUCCESSFUL}";                        
+                        labelGeneralStatus.Text = $"Connection {ConnectionStatus.SUCCESSFUL}";
                         labelLatestUpdate.Text = $"Last update: {DateTime.Now.ToLongTimeString()}";
                         labelStatusBar.Text = "";
                         generalProgressStatus.Value = 0;
@@ -502,7 +509,9 @@ namespace BreCalClient
                     }
 
                     this.FilterShipcalls();
-                    this.UpdateUI();                    
+                    await uiLock.WaitAsync();
+                    this.UpdateUI();
+                    uiLock.Release();
                 }
 
                 try
@@ -665,14 +674,14 @@ namespace BreCalClient
             {
                 _ = this._visibleControlModels.RemoveAll(x =>
                 {
-                    Times? t = x.GetTimesForParticipantType(ParticipantType.AGENCY);                    
+                    Times? t = x.GetTimesForParticipantType(ParticipantType.AGENCY);
                     switch (x.Shipcall?.Type)
                     {
                         case ShipcallType.Arrival:
-                            {                                
+                            {
                                 if ((t != null) && t.EtaBerth.HasValue) return t.EtaBerth.Value < sfm.EtaFrom;
                                 return x.Shipcall?.Eta < sfm.EtaFrom;
-                            }                            
+                            }
                         default: // Shifting / Departing
                             {
                                 if ((t != null) && t.EtdBerth.HasValue) return t.EtdBerth.Value < sfm.EtaFrom;
@@ -689,7 +698,7 @@ namespace BreCalClient
                     Times? t = x.GetTimesForParticipantType(ParticipantType.AGENCY);
                     DateTime refValue = sfm.EtaTo.Value.AddMinutes(1439); // 23:59
                     switch (x.Shipcall?.Type)
-                    {                        
+                    {
                         case ShipcallType.Arrival:
                             {
                             if ((t != null) && t.EtaBerth.HasValue) return t.EtaBerth.Value > refValue;
@@ -701,7 +710,7 @@ namespace BreCalClient
                             return x.Shipcall?.Etd > refValue;
                         }
                     }
-                });                
+                });
             }
 
             if(sfm.MineOnly ?? false)
@@ -765,7 +774,7 @@ 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
                 {
@@ -785,7 +794,7 @@ namespace BreCalClient
                 }
                 finally
                 {
-                    _uiUpdateRunning = 0;
+                   // _uiUpdateRunning = 0;
                 }
 
                 Mouse.OverrideCursor = null;
@@ -991,6 +1000,6 @@ namespace BreCalClient
         }
 
         #endregion
-       
+
     }
 }