diff --git a/Pilz/Data/Json/JsonDataContainer.cs b/Pilz/Data/Json/JsonDataContainer.cs
index f178339..1bd9568 100644
--- a/Pilz/Data/Json/JsonDataContainer.cs
+++ b/Pilz/Data/Json/JsonDataContainer.cs
@@ -9,21 +9,27 @@ public abstract class JsonDataContainer
 
     public virtual HashSet<T>? Set<T>(bool allowCreate) where T : class, IDataObject
     {
-        var list = sets.OfType<HashSet<T>>().FirstOrDefault();
-
-        if (list == null && allowCreate)
+        lock (sets)
         {
-            list = [];
-            sets.Add(list);
-        }
+            var list = sets.OfType<HashSet<T>>().FirstOrDefault();
 
-        return list;
+            if (list == null && allowCreate)
+            {
+                list = [];
+                sets.Add(list);
+            }
+
+            return list;
+        }
     }
 
     public virtual void CopyTo(JsonDataContainer container)
     {
-        foreach (var set in sets)
-            container.sets.Add(set);
+        lock (sets)
+        {
+            foreach (var set in sets)
+                container.sets.Add(set);
+        }
     }
 
     protected virtual JsonSerializer GetSerializer()
diff --git a/Pilz/Data/Json/JsonDataManager.cs b/Pilz/Data/Json/JsonDataManager.cs
index d0f95df..7765779 100644
--- a/Pilz/Data/Json/JsonDataManager.cs
+++ b/Pilz/Data/Json/JsonDataManager.cs
@@ -21,9 +21,7 @@ public class JsonDataManager(JsonDataContainer container) : DataManager
 
     protected override void UpdateEntity<T>(T obj)
     {
-        var set = container.Set<T>(true);
-        if (!set.Contains(obj))
-            set.Add(obj);
+        container.Set<T>(true).Add(obj);
     }
 
     protected override void SaveChanges()
diff --git a/Pilz/Data/Json/JsonFileContainer.cs b/Pilz/Data/Json/JsonFileContainer.cs
index 8417a55..c8b5abf 100644
--- a/Pilz/Data/Json/JsonFileContainer.cs
+++ b/Pilz/Data/Json/JsonFileContainer.cs
@@ -2,15 +2,23 @@
 
 public class JsonFileContainer(string filePath) : JsonDataContainer
 {
+    protected readonly object _lock_FileAction = new();
+
     public override void Read()
     {
-        using var sw = new StreamReader(filePath);
-        GetSerializer().Populate(sw, this);
+        lock (_lock_FileAction)
+        {
+            using var sw = new StreamReader(filePath);
+            GetSerializer().Populate(sw, this);
+        }
     }
 
     public override void Flush()
     {
-        using var sw = new StreamWriter(filePath, false);
-        GetSerializer().Serialize(sw, this);
+        lock (_lock_FileAction)
+        {
+            using var sw = new StreamWriter(filePath, false);
+            GetSerializer().Serialize(sw, this);
+        }
     }
 }
diff --git a/Pilz/Data/Json/JsonStreamContainer.cs b/Pilz/Data/Json/JsonStreamContainer.cs
index 359c2e1..ce5876f 100644
--- a/Pilz/Data/Json/JsonStreamContainer.cs
+++ b/Pilz/Data/Json/JsonStreamContainer.cs
@@ -2,18 +2,25 @@
 
 public class JsonStreamContainer(Stream stream) : JsonDataContainer
 {
+    protected readonly object _lock_StreamAction = new();
     public override void Read()
     {
-        using var sw = new StreamReader(stream);
-        stream.Position = 0;
-        GetSerializer().Populate(sw, this);
+        lock (_lock_StreamAction)
+        {
+            using var sw = new StreamReader(stream);
+            stream.Position = 0;
+            GetSerializer().Populate(sw, this);
+        }
     }
 
     public override void Flush()
     {
-        using var sw = new StreamWriter(stream);
-        stream.Position = 0;
-        GetSerializer().Serialize(sw, this);
-        stream.SetLength(stream.Position);
+        lock (_lock_StreamAction)
+        {
+            using var sw = new StreamWriter(stream);
+            stream.Position = 0;
+            GetSerializer().Serialize(sw, this);
+            stream.SetLength(stream.Position);
+        }
     }
 }
diff --git a/Pilz/Pilz.csproj b/Pilz/Pilz.csproj
index 6fce36d..04096b6 100644
--- a/Pilz/Pilz.csproj
+++ b/Pilz/Pilz.csproj
@@ -5,7 +5,7 @@
     <LangVersion>latest</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>annotations</Nullable>
-    <Version>2.4.2</Version>
+    <Version>2.4.3</Version>
   </PropertyGroup>
   
   <ItemGroup>