diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Group.java b/src/main/java/nl/connectedit/swiss/domain/entity/Group.java
index a00aeb8..6e0638c 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Group.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Group.java
@@ -33,12 +33,12 @@ public class Group extends AbstractEntity {
   @OrderBy("name")
   private List<Round> rounds;
 
-  @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
+  @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE}, fetch = FetchType.LAZY)
   @JoinTable(
     name = "eventgroup_teams",
     joinColumns = @JoinColumn(name = "group_id"),
     inverseJoinColumns = @JoinColumn(name = "teams_id")
   )
-  private List<Team> teams;
+  private List<Team> teams = new ArrayList<>();
 
 }
diff --git a/src/main/java/nl/connectedit/swiss/domain/entity/Team.java b/src/main/java/nl/connectedit/swiss/domain/entity/Team.java
index 674365a..f77e345 100644
--- a/src/main/java/nl/connectedit/swiss/domain/entity/Team.java
+++ b/src/main/java/nl/connectedit/swiss/domain/entity/Team.java
@@ -2,6 +2,7 @@ package nl.connectedit.swiss.domain.entity;
 
 import jakarta.annotation.Nullable;
 import jakarta.persistence.*;
+import java.util.ArrayList;
 import java.util.List;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
@@ -19,7 +20,7 @@ public class Team extends AbstractEntity {
     private Long id;
 
     @ManyToMany(mappedBy = "teams", fetch = FetchType.LAZY)
-    private List<Group> groups;
+    private List<Group> groups = new ArrayList<>();
 
     @ManyToOne
     private Player player1;
diff --git a/src/main/java/nl/connectedit/swiss/service/TournamentDivideService.java b/src/main/java/nl/connectedit/swiss/service/TournamentDivideService.java
index fd5d9b4..8bd6aab 100644
--- a/src/main/java/nl/connectedit/swiss/service/TournamentDivideService.java
+++ b/src/main/java/nl/connectedit/swiss/service/TournamentDivideService.java
@@ -1,9 +1,5 @@
 package nl.connectedit.swiss.service;
 
-import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.datatype.jsr310.JSR310Module;
-import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import jakarta.transaction.Transactional;
 import java.util.ArrayList;
 import java.util.Comparator;
@@ -49,19 +45,8 @@ public class TournamentDivideService {
 
     tournament.setStatus(TournamentStatus.DIVIDED);
 
-//    var mapper = new ObjectMapper();
-//    mapper.registerModule(new JavaTimeModule());
-//    try {
-//      log.info(mapper.writeValueAsString(tournament));
-//    } catch (JsonProcessingException e) {
-//      throw new RuntimeException(e);
-//    }
     tournamentRepository.save(tournament);
-//    try {
-//      log.info(mapper.writeValueAsString(tournament));
-//    } catch (JsonProcessingException e) {
-//      throw new RuntimeException(e);
-//    }
+
     return tournament;
   }
 
@@ -111,7 +96,8 @@ public class TournamentDivideService {
     group.setTeams(new ArrayList<>());
     log.info("getGroup: aantal registrations = " + registrations.size());
     for (var registration : registrations) {
-      group.getTeams().add(getTeam(registration, group));
+//      group.getTeams().add(getTeam(registration, group));
+      addTeamToGroup(registration, group);
       log.info("in getGroup-loop; groepgrootte = " + group.getTeams().size());
     }
 
@@ -119,6 +105,8 @@ public class TournamentDivideService {
   }
 
   private List<Group> getGroups(List<Registration> orgRegistrations, EventType type) {
+    var groups = new ArrayList<Group>();
+
     var registrations = new ArrayList<>(orgRegistrations);
 
     var group1 = new Group();
@@ -161,18 +149,28 @@ public class TournamentDivideService {
       group2.getTeams().removeLast();
     }
 
-    return List.of(group1, group2);
+    groups.add(group1);
+    groups.add(group2);
+    return groups;
   }
 
   private Team getTeam(Registration registration, Group group) {
     var team = new Team();
     team.setPlayer1(registration.getPlayer());
     team.setPlayer2(registration.getPartner());
-    team.setGroups(List.of(group));
+    team.getGroups().add(group);
 
     return team;
   }
 
+  private void addTeamToGroup(Registration registration, Group group) {
+    var team = new Team();
+    team.setPlayer1(registration.getPlayer());
+    team.setPlayer2(registration.getPartner());
+    team.getGroups().add(group);
+    group.getTeams().add(team);
+  }
+
   public Tournament clear(Tournament tournament) {
     for (var event : tournament.getEvents()) {
       event.getGroups().clear();