Program: 80864
Project: 80864
Buggy source:
@Override public PacketListenerResult onTeamPacket(Team packet){
  if (fakePlayerUsernameSet.contains(packet.getName())) {
    throw new AssertionError("String_Node_Str" + packet);
  }
  if (packet.getMode() == 1) {
    net.md_5.bungee.api.score.Team team=serverTeams.remove(packet.getName());
    for (    String player : team.getPlayers()) {
      playerToTeamMap.remove(player,team.getName());
      if (!passtrough && size != 80 && nameToSlotMap.containsKey(player)) {
        Team packet1=new Team();
        packet1.setMode((byte)2);
        packet1.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
        packet1.setDisplayName(packet1.getName());
        packet1.setPrefix("String_Node_Str");
        packet1.setSuffix("String_Node_Str");
        packet1.setFriendlyFire((byte)1);
        packet1.setNameTagVisibility("String_Node_Str");
        if (teamCollisionRuleSupported) {
          packet1.setCollisionRule("String_Node_Str");
        }
        packet1.setColor((byte)0);
        sendPacket(packet1);
      }
    }
  }
 else {
    net.md_5.bungee.api.score.Team t;
    if (packet.getMode() == 0) {
      t=new net.md_5.bungee.api.score.Team(packet.getName());
      serverTeams.put(packet.getName(),t);
    }
 else {
      t=serverTeams.get(packet.getName());
    }
    if (t != null) {
      if (packet.getMode() == 0 || packet.getMode() == 2) {
        t.setDisplayName(packet.getDisplayName());
        t.setPrefix(packet.getPrefix());
        t.setSuffix(packet.getSuffix());
        t.setFriendlyFire(packet.getFriendlyFire());
        t.setNameTagVisibility(packet.getNameTagVisibility());
        if (teamCollisionRuleSupported) {
          t.setCollisionRule(packet.getCollisionRule());
        }
        t.setColor(packet.getColor());
      }
      if (packet.getPlayers() != null) {
        for (        String s : packet.getPlayers()) {
          if (packet.getMode() == 0 || packet.getMode() == 3) {
            if (playerToTeamMap.containsKey(s)) {
              serverTeams.get(playerToTeamMap.get(s)).getPlayers().remove(s);
            }
            t.addPlayer(s);
            playerToTeamMap.put(s,t.getName());
          }
 else {
            t.removePlayer(s);
            playerToTeamMap.remove(s,t.getName());
          }
        }
      }
    }
  }
  if (passtrough || size == 80) {
    return PacketListenerResult.PASS;
  }
  if (packet.getMode() == 2) {
    for (    String player : serverTeams.get(packet.getName()).getPlayers()) {
      if (nameToSlotMap.containsKey(player)) {
        Team team=new Team();
        team.setMode((byte)2);
        team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
        team.setDisplayName(packet.getDisplayName());
        team.setPrefix(packet.getPrefix());
        team.setSuffix(packet.getSuffix());
        team.setFriendlyFire(packet.getFriendlyFire());
        team.setNameTagVisibility(packet.getNameTagVisibility());
        if (teamCollisionRuleSupported) {
          team.setCollisionRule(packet.getCollisionRule());
        }
        team.setColor(packet.getColor());
        sendPacket(team);
      }
    }
  }
  boolean modified=false;
  if (packet.getMode() == 0 || packet.getMode() == 3 || packet.getMode() == 4) {
    int length=0;
    for (    String player : packet.getPlayers()) {
      if (!nameToSlotMap.containsKey(player)) {
        length++;
      }
 else {
        if (packet.getMode() == 4 && nameToSlotMap.containsKey(player)) {
          Team team=new Team();
          team.setMode((byte)2);
          team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
          team.setDisplayName(team.getName());
          team.setPrefix("String_Node_Str");
          team.setSuffix("String_Node_Str");
          team.setFriendlyFire((byte)1);
          team.setNameTagVisibility("String_Node_Str");
          if (teamCollisionRuleSupported) {
            team.setCollisionRule("String_Node_Str");
          }
          team.setColor((byte)0);
          sendPacket(team);
        }
 else         if (nameToSlotMap.containsKey(player)) {
          net.md_5.bungee.api.score.Team serverTeam=serverTeams.get(playerToTeamMap.get(player));
          Team team=new Team();
          team.setMode((byte)2);
          team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
          team.setDisplayName(serverTeam.getDisplayName());
          team.setPrefix(serverTeam.getPrefix());
          team.setSuffix(serverTeam.getSuffix());
          team.setFriendlyFire(serverTeam.getFriendlyFire());
          team.setNameTagVisibility(serverTeam.getNameTagVisibility());
          if (teamCollisionRuleSupported) {
            team.setCollisionRule(serverTeam.getCollisionRule());
          }
          team.setColor(serverTeam.getColor());
          sendPacket(team);
        }
      }
    }
    if (length != packet.getPlayers().length) {
      String[] players=new String[length];
      length=0;
      for (      String player : packet.getPlayers()) {
        if (!nameToSlotMap.containsKey(player)) {
          players[length++]=player;
        }
      }
      packet.setPlayers(players);
      modified=true;
    }
  }
  return modified ? PacketListenerResult.MODIFIED : PacketListenerResult.PASS;
}

Fixed version (ground truth):
@Override public PacketListenerResult onTeamPacket(Team packet){
  if (fakePlayerUsernameSet.contains(packet.getName())) {
    throw new AssertionError("String_Node_Str" + packet);
  }
  if (packet.getMode() == 1) {
    net.md_5.bungee.api.score.Team team=serverTeams.remove(packet.getName());
    if (team != null) {
      for (      String player : team.getPlayers()) {
        playerToTeamMap.remove(player,team.getName());
        if (!passtrough && size != 80 && nameToSlotMap.containsKey(player)) {
          Team packet1=new Team();
          packet1.setMode((byte)2);
          packet1.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
          packet1.setDisplayName(packet1.getName());
          packet1.setPrefix("String_Node_Str");
          packet1.setSuffix("String_Node_Str");
          packet1.setFriendlyFire((byte)1);
          packet1.setNameTagVisibility("String_Node_Str");
          if (teamCollisionRuleSupported) {
            packet1.setCollisionRule("String_Node_Str");
          }
          packet1.setColor((byte)0);
          sendPacket(packet1);
        }
      }
    }
  }
 else {
    net.md_5.bungee.api.score.Team t;
    if (packet.getMode() == 0) {
      t=new net.md_5.bungee.api.score.Team(packet.getName());
      serverTeams.put(packet.getName(),t);
    }
 else {
      t=serverTeams.get(packet.getName());
    }
    if (t != null) {
      if (packet.getMode() == 0 || packet.getMode() == 2) {
        t.setDisplayName(packet.getDisplayName());
        t.setPrefix(packet.getPrefix());
        t.setSuffix(packet.getSuffix());
        t.setFriendlyFire(packet.getFriendlyFire());
        t.setNameTagVisibility(packet.getNameTagVisibility());
        if (teamCollisionRuleSupported) {
          t.setCollisionRule(packet.getCollisionRule());
        }
        t.setColor(packet.getColor());
      }
      if (packet.getPlayers() != null) {
        for (        String s : packet.getPlayers()) {
          if (packet.getMode() == 0 || packet.getMode() == 3) {
            if (playerToTeamMap.containsKey(s)) {
              serverTeams.get(playerToTeamMap.get(s)).removePlayer(s);
            }
            t.addPlayer(s);
            playerToTeamMap.put(s,t.getName());
          }
 else {
            t.removePlayer(s);
            playerToTeamMap.remove(s,t.getName());
          }
        }
      }
    }
  }
  if (passtrough || size == 80) {
    return PacketListenerResult.PASS;
  }
  if (packet.getMode() == 2) {
    for (    String player : serverTeams.get(packet.getName()).getPlayers()) {
      if (nameToSlotMap.containsKey(player)) {
        Team team=new Team();
        team.setMode((byte)2);
        team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
        team.setDisplayName(packet.getDisplayName());
        team.setPrefix(packet.getPrefix());
        team.setSuffix(packet.getSuffix());
        team.setFriendlyFire(packet.getFriendlyFire());
        team.setNameTagVisibility(packet.getNameTagVisibility());
        if (teamCollisionRuleSupported) {
          team.setCollisionRule(packet.getCollisionRule());
        }
        team.setColor(packet.getColor());
        sendPacket(team);
      }
    }
  }
  boolean modified=false;
  if (packet.getMode() == 0 || packet.getMode() == 3 || packet.getMode() == 4) {
    int length=0;
    for (    String player : packet.getPlayers()) {
      if (!nameToSlotMap.containsKey(player)) {
        length++;
      }
 else {
        if (packet.getMode() == 4 && nameToSlotMap.containsKey(player)) {
          Team team=new Team();
          team.setMode((byte)2);
          team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
          team.setDisplayName(team.getName());
          team.setPrefix("String_Node_Str");
          team.setSuffix("String_Node_Str");
          team.setFriendlyFire((byte)1);
          team.setNameTagVisibility("String_Node_Str");
          if (teamCollisionRuleSupported) {
            team.setCollisionRule("String_Node_Str");
          }
          team.setColor((byte)0);
          sendPacket(team);
        }
 else         if (nameToSlotMap.containsKey(player)) {
          net.md_5.bungee.api.score.Team serverTeam=serverTeams.get(playerToTeamMap.get(player));
          Team team=new Team();
          team.setMode((byte)2);
          team.setName(fakePlayerUsernames[nameToSlotMap.get(player)]);
          team.setDisplayName(serverTeam.getDisplayName());
          team.setPrefix(serverTeam.getPrefix());
          team.setSuffix(serverTeam.getSuffix());
          team.setFriendlyFire(serverTeam.getFriendlyFire());
          team.setNameTagVisibility(serverTeam.getNameTagVisibility());
          if (teamCollisionRuleSupported) {
            team.setCollisionRule(serverTeam.getCollisionRule());
          }
          team.setColor(serverTeam.getColor());
          sendPacket(team);
        }
      }
    }
    if (length != packet.getPlayers().length) {
      String[] players=new String[length];
      length=0;
      for (      String player : packet.getPlayers()) {
        if (!nameToSlotMap.containsKey(player)) {
          players[length++]=player;
        }
      }
      packet.setPlayers(players);
      modified=true;
    }
  }
  return modified ? PacketListenerResult.MODIFIED : PacketListenerResult.PASS;
}