Redis data returned is not what was expected

Using this code:

private string GetKeyForId(int idShipmentRequest)
{
  return $"{key}:{idShipmentRequest}";
}

public DTO.AnnouncedShipment GetById(int id)
{
    using (var client = manager.GetClient())
    {
      var announcedShipments = client.As<DTO.AnnouncedShipment>();
      var key = GetKeyForId(id);
      var announcedShipment = announcedShipments.GetValue(key);
      logger.Info($"GetById for id: {id}. Key: {key}. Announced: {announcedShipment.Dump()}");
      return announcedShipment;
    }
}

we sometime see this in our log:

2019-11-05 12:24:46.0095||ShipmentLogger|INFO|GetById for id: 14443493. Key: AnnouncedShipment:14443493. Announced: {
	idShipmentRequest: 14443493,
	idContact: 65178992,
	idCampagne: 1921,
	packingDetails: 
	[
		{
			idPackingType: 3,
			numberOfItems: 2
			....

This is correct, since the so called idSHipmentRequest should be identical to the id we get the value for.
But sometimes we see this - the same request, different result:

2019-11-05 14:11:14.1342||ShipmentLogger|INFO|GetById for id: 14443493. Key: AnnouncedShipment:14443493. Announced: {
	idShipmentRequest: 14460000,
	idContact: 64795584,
	idCampagne: 1088,
	packingDetails: 
	[
		{
			idPackingType: 4,
			numberOfItems: 2
			...

What can cause this? Is this a REDIS issue? Of could it be ServiceStack?

Couldn’t tell you, it’s just reporting what’s stored in Redis, have you verified against what’s stored in Redis?

Yes, I verified and double checked. In fact, we have been hunting this ‘feature’ for a couple of months and it happens every now and then. We are now actively monitoring REDIS as well to see if the data returned is actually the wrong value, or if the issue lies with the RedisClient.
Either way, it seems to be a buffering thing. Reason I suspect buffering is that the data returned in a consecutive call to this or another pooled client yields the data for the past request. So basically, if we ask data for 1, 2, 3, 4, 5 we sometimes get 2, 3, 4, 5.
Still looking into this, but it’s not something you have seen before?

No, I’ve no idea of what the underlying cause could be.