Django Channels stops working with self.receive_lock.locked error

I'm struggling with a problem using Django Channels to make a notification system. It works fine in local. In production (on Webfaction), it will work for fine for a few minutes, and then stop working with the following error message:

ERROR - server - Exception inside application: 
  File "/home/client/.virtualenvs/project/lib/python3.6/site-packages/channels/sessions.py", line 175, in __call__
    return await self.inner(receive, self.send)
  File "/home/client/.virtualenvs/project/lib/python3.6/site-packages/channels/middleware.py", line 41, in coroutine_call
await inner_instance(receive, send)
  File "/home/client/.virtualenvs/project/lib/python3.6/site-packages/channels/consumer.py", line 54, in __call__
await await_many_dispatch([receive, self.channel_receive], self.dispatch)
  File "/home/client/.virtualenvs/project/lib/python3.6/site-packages/channels/utils.py", line 57, in await_many_dispatch
await task
  File "/home/client/.virtualenvs/project/lib/python3.6/site-packages/channels_redis/core.py", line 400, in receive
assert not self.receive_lock.locked()

I'm using:

• aioredis==1.1.0
• asgiref=2.3.2
• channels==2.1.3
• channels-redis==2.3.0
• django==2.1.2
• Redis 4.0.11
• Python 3.6.6

This is all using django's development server.

My consumer looks like this:

class NotificationConsumer (AsyncJsonWebsocketConsumer):
    slight_ordering = True

    async def connect (self):
        self.user = self.scope["user"]
        await self.accept()
        group_name = "notifications_{}".format(self.user.employee.pk)
        await self.channel_layer.group_add(group_name, self.channel_name)

    async def disconnect (self, code):
        self.user = self.scope["user"]
        group_name = "notifications_{}".format(self.user.employee.pk)
        await self.channel_layer.group_discard (group_name, self.channel_name)

    async def user_notification (self, event):
        await self.send_json(event)

The notification is sent when created, using a post_save signal:

@receiver(post_save, sender=Notification)
def new_notification (sender, instance, **kwargs):
    channel_layer = get_channel_layer()
    group_name = "notifications_{}".format(instance.employee.pk)
    async_to_sync(channel_layer.group_send)(
       group_name, {
           "type": "user.notification",
           "event": "New notification",
           "notification_pk": instance.pk,
       }
    )

My routing looks like this:

application = ProtocolTypeRouter({
    'websocket': AuthMiddlewareStack(
        URLRouter(
            [url(r'^notifications/$', NotificationConsumer),]
        )
    ),
})

And finally, I'm using WebSocketBridge on the frontend:

const webSocketBridge = new channels.WebSocketBridge();
webSocketBridge.connect('/notifications/');
webSocketBridge.listen(function(action, stream){
   //show the notification
});

If anyone has an idea of what could be happening and why I get this self.receive_lock.locked() error, I'd appreciate it a lot.

Thanks