Issues with MessagingCenter

I've been having some strange problems with MessagingCenter. Sometimes calling MessagingCenter.Send() does not return.

An example in my code is:

Tiles = td.TileLayoutInstances.Select(x => new Tile(x)).OrderBy(x => x.SortOrder).ToList();
SubscribeToTiles(Tiles);
Debug.WriteLine("Sending QrLoaded");
MessagingCenter.Send<object, bool>(new object(), "QrCodeLoaded", true);
Debug.WriteLine("Sent QrLoaded");

"Sent QrLoaded" never occurs

Any tips would be welcome