AKKA.NET randomly sends messages to deadletters

I have an actor system that randomly fails because of messages being delivered to dead letters. Fail meaning it just does not complete

Message [UploadFileFromDropboxSuccessMessage] from akka://MySystem-Actor-System/user/...../DropboxToBlobSourceSubmissionUploaderActor/DropboxToBlobSourceFileUploaderActor--1 to akka://MySystem-Actor-System/user/.../DropboxToBlobSourceSubmissionUploaderActor was not delivered. [5] dead letters encountered .This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.

private void InitialState()
{
    Receive<UploadFileFromDropboxMessage>(msg =>
    {
        var sender = Sender;
        var self = Self;
        var parent = Parent;
        var logger = Logger;
        UploadFromDropboxToBlobStorageAsync(msg.File, msg.RelativeSourceRootDirectory, msg.BlobStorageDestinationRootPath).ContinueWith(o =>
        {
            if (!o.IsFaulted)
            {
                parent.Tell(new UploadFileFromDropboxSuccessMessage(msg.File.Path, o.Result), self);
            }
            else
            {
                parent.Tell(new UploadFileFromDropboxFailureMessage(msg.File.Path), self);

            }
        }, TaskContinuationOptions.ExecuteSynchronously);
    });
}

I also tried

private void InitialState()
{
    Receive<UploadFileFromDropboxMessage>(msg =>
    {
        try
        {
            var result = UploadFromDropboxToBlobStorageAsync(msg.File, msg.RelativeSourceRootDirectory, msg.BlobStorageDestinationRootPath).Result;
            Parent.Tell(new UploadFileFromDropboxSuccessMessage(msg.File.Path, result));
        }
        catch (Exception ex)
        {
            Parent.Tell(new UploadFileFromDropboxFailureMessage(msg.File.Path, ex));
        }
    });
}

This happens randomly and happens on both success and complete. I have checked parent.IsNobody()... and this returns false. In the documentation it says that alocal actor can fail:

• if the mailbox does not accept the message (e.g. full BoundedMailbox)
• if the receiving actor fails while processing the message or is already terminated

I can't imagine a use case where this is true but also don't really know how to check from the context of my current actor (even if its just for logging purposes).

EDIT: Does AKKA have a limitation on the total amount of messages in the entire system?

EDIT: This happens 1 would say 10% of the time.

EDIT: Eventually discovered it was an actor waaay higher in the tree being killed. I am still confused why IsNobody() returned false if its in deed dead.