diff --git a/wise-webapp/src/main/java/com/wisemapping/model/Collaboration.java b/wise-webapp/src/main/java/com/wisemapping/model/Collaboration.java
index 7446b6f5..630776f9 100644
--- a/wise-webapp/src/main/java/com/wisemapping/model/Collaboration.java
+++ b/wise-webapp/src/main/java/com/wisemapping/model/Collaboration.java
@@ -26,6 +26,7 @@ import org.jetbrains.annotations.Nullable;
 import javax.persistence.*;
 import javax.validation.constraints.NotNull;
 import java.io.Serializable;
+import java.util.Objects;
 
 @Entity
 @Table(name = "COLLABORATION")
@@ -127,16 +128,14 @@ public class Collaboration implements Serializable {
         Collaboration that = (Collaboration) o;
 
         if (id != that.id) return false;
-        if (collaborator != null ? !collaborator.equals(that.collaborator) : that.collaborator != null) return false;
-        if (mindMap != null ? !mindMap.equals(that.mindMap) : that.mindMap != null) return false;
+        if (!Objects.equals(collaborator, that.collaborator)) return false;
+        if (!Objects.equals(mindMap, that.mindMap)) return false;
         return role == that.role;
     }
 
     @Override
     public int hashCode() {
-        int result = id ^ (id >>> 32);
-        result = 31 * result + (role != null ? role.hashCode() : 0);
-        result = 31 * result + (mindMap != null ? mindMap.hashCode() : 0);
-        return result;
+        //https://thorben-janssen.com/ultimate-guide-to-implementing-equals-and-hashcode-with-hibernate/
+        return 13;
     }
 }
diff --git a/wise-webapp/src/main/java/com/wisemapping/model/Label.java b/wise-webapp/src/main/java/com/wisemapping/model/Label.java
index 95e80415..6126560d 100644
--- a/wise-webapp/src/main/java/com/wisemapping/model/Label.java
+++ b/wise-webapp/src/main/java/com/wisemapping/model/Label.java
@@ -24,6 +24,7 @@ import org.jetbrains.annotations.Nullable;
 
 import javax.persistence.*;
 import java.io.Serializable;
+import java.util.Objects;
 
 @Entity
 @Table(name = "LABEL")
@@ -34,17 +35,22 @@ public class Label implements Serializable {
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private int id;
 
-    @NotNull private String title;
-    @NotNull private String color;
-    @Nullable private String iconName;
+    @NotNull
+    private String title;
+    @NotNull
+    private String color;
+    @Nullable
+    private String iconName;
 
     @ManyToOne(fetch = FetchType.LAZY)
-    @JoinColumn(name="creator_id",nullable = true,unique = true)
-    @NotNull private User creator;
+    @JoinColumn(name = "creator_id", nullable = true, unique = true)
+    @NotNull
+    private User creator;
 
     @ManyToOne(fetch = FetchType.LAZY)
-    @JoinColumn(name="parent_label_id",nullable = true)
-    @Nullable private Label parent;
+    @JoinColumn(name = "parent_label_id", nullable = true)
+    @Nullable
+    private Label parent;
 
     public void setParent(@Nullable Label parent) {
         this.parent = parent;
@@ -104,17 +110,15 @@ public class Label implements Serializable {
         if (this == o) return true;
         if (!(o instanceof Label)) return false;
 
-        Label label = (Label) o;
-
+        final Label label = (Label) o;
         return id == label.id && creator.getId() == label.creator.getId()
-                &&  !(parent != null ? !parent.equals(label.parent) : label.parent != null);
+                && Objects.equals(parent, label.parent);
     }
 
     @Override
     public int hashCode() {
-        long result = id;
-        result = 31 * result + title.hashCode();
-        result = 31 * result + (creator!=null?creator.hashCode():0);
+        long result = title.hashCode();
+        result = 31 * result + (creator != null ? creator.hashCode() : 0);
         result = 31 * result + (parent != null ? parent.hashCode() : 0);
         return (int) result;
     }
diff --git a/wise-webapp/src/main/java/com/wisemapping/model/Mindmap.java b/wise-webapp/src/main/java/com/wisemapping/model/Mindmap.java
index d3cdf366..0b2052ff 100644
--- a/wise-webapp/src/main/java/com/wisemapping/model/Mindmap.java
+++ b/wise-webapp/src/main/java/com/wisemapping/model/Mindmap.java
@@ -146,7 +146,9 @@ public class Mindmap implements Serializable {
     }
 
     public void removedCollaboration(@NotNull Collaboration collaboration) {
-        collaborations.remove(collaboration);
+        // https://stackoverflow.com/questions/25125210/hibernate-persistentset-remove-operation-not-working
+        this.collaborations.remove(collaboration);
+        collaboration.setMindMap(null);
     }
 
     public void removedCollaboration(@NotNull Set<Collaboration> collaborations) {
diff --git a/wise-webapp/src/main/java/com/wisemapping/security/aop/ViewBaseSecurityAdvise.java b/wise-webapp/src/main/java/com/wisemapping/security/aop/ViewBaseSecurityAdvise.java
index c9807d61..52c59944 100755
--- a/wise-webapp/src/main/java/com/wisemapping/security/aop/ViewBaseSecurityAdvise.java
+++ b/wise-webapp/src/main/java/com/wisemapping/security/aop/ViewBaseSecurityAdvise.java
@@ -38,7 +38,6 @@ public class ViewBaseSecurityAdvise
 
     @Override
     protected boolean isAllowed(@Nullable User user, Mindmap map) {
-        System.out.println("VIEWWWWWWWWWWWWW");
         return getMindmapService().hasPermissions(user, map, CollaborationRole.VIEWER);
     }
 
diff --git a/wise-webapp/src/main/java/com/wisemapping/service/MindmapServiceImpl.java b/wise-webapp/src/main/java/com/wisemapping/service/MindmapServiceImpl.java
index 8207a662..7a4a763f 100755
--- a/wise-webapp/src/main/java/com/wisemapping/service/MindmapServiceImpl.java
+++ b/wise-webapp/src/main/java/com/wisemapping/service/MindmapServiceImpl.java
@@ -143,15 +143,13 @@ public class MindmapServiceImpl
     public void removeCollaboration(@NotNull Mindmap mindmap, @NotNull Collaboration collaboration) throws CollaborationException {
         // remove collaborator association
         final Mindmap mindMap = collaboration.getMindMap();
-        final Set<Collaboration> collaborations = mindMap.getCollaborations();
-
         final User creator = mindMap.getCreator();
         if (creator.identityEquality(collaboration.getCollaborator())) {
             throw new CollaborationException("User is the creator and must have ownership permissions.Creator Email:" + mindMap.getCreator().getEmail() + ",Collaborator:" + collaboration.getCollaborator().getEmail());
         }
 
         // When you delete an object from hibernate you have to delete it from *all* collections it exists in...
-        collaborations.remove(collaboration);
+        mindMap.removedCollaboration(collaboration);
         mindmapManager.removeCollaboration(collaboration);
     }
 
@@ -249,7 +247,7 @@ public class MindmapServiceImpl
 
     @Override
     public void revertChange(@NotNull Mindmap mindmap, int historyId)
-            throws WiseMappingException, IOException {
+            throws WiseMappingException {
         final MindMapHistory history = mindmapManager.getHistory(historyId);
         mindmap.setZippedXml(history.getZippedXml());
         updateMindmap(mindmap, true);