Pusher filling up with Laravel Broadcasts

Recently been observing this in our Laravel project that Pusher is getting clogged up with messages upto the limit. This is abnormal for usage of peak concurrent - 16 and 4 million messages a day.

Going through the Pusher dashboard, below is the extent of the damage being done.

There is a specific pattern of usage. When I turn off the supervisord worker, the graph stops and when I start the worker again, it comes back up in a predictable pattern shown in the graph below.

Below is a sample message I got when running redis-cli monitor.

As you can see above, the index [attempts] is 69507. Does that mean that this event has been broadasted 69507 times ? Why would an event be broadcasted so many times ? When does an event stop being broadcasted ? Am I doing something wrong ?

Here is the code for the AgendaParticipantUpdated event. Would be great if there is something fundamentally wrong in the way the event has been implemented.

<?php

namespace App\Events;

use App\AgendaParticipant;
use App\Agenda;
use Illuminate\Queue\SerializesModels;
use Illuminate\Broadcasting\PrivateChannel;
use Illuminate\Foundation\Events\Dispatchable;
use Illuminate\Broadcasting\InteractsWithSockets;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;

class AgendaParticipantUpdated implements ShouldBroadcast
{
    use Dispatchable, InteractsWithSockets, SerializesModels;

    /** @var agendaParticipant */
    public $agendaParticipant;

    /**
     * Create a new event instance.
     *
     * @param AgendaParticipant $agendaParticipant
     */
    public function __construct(AgendaParticipant $agendaParticipant)
    {
        $this->agendaParticipant = $agendaParticipant;
    }

    /**
     * Get the channels the event should broadcast on.
     *
     * @return \Illuminate\Broadcasting\Channel|array
     */
    public function broadcastOn()
    {
        return new PrivateChannel("meetings.{$this->agendaParticipant->agenda->meeting->id}");
    }

    /**
     * Get the data to broadcast.
     *
     * @return array
     */
    public function broadcastWith()
    {
        $agenda = Agenda::where('id', $this->agendaParticipant->agenda->id)->first();
        $agenda->load(['participants' => function ($query) {
            $query->orderBy('order')->orderBy('id');
        }, 'participants.member.user']);

        return [
            'agendaParticipant' => $this->agendaParticipant,
            'agenda' => $agenda,
        ];
    }
}

Would appreciate any help on this since it is interfering with our daily operations.

via Chebli Mohamed