My !gnusocial log was freaking out with the following errors being reported several times a second in a block of 4 messages:

DBQueueManager (main): [xmpp:Notice 12990] Failed to handle item
claiming queue item id = 15160 for transport xmpp
implugin.php - Sending notice 12990 to <redacted xmpp account>
DBQueueManager (main): [xmpp:Notice 12990] Exception thrown: Notice has no object type.

In the db queue_item table I saw the row generating it.

id: 15160 framedata: <snip> transport: xmpp createddate: 2016-02-07 11:24:09

Other xmpp messages were coming in at the same time and being processed successfully but their transport was "xmpp-out" not "xmpp". Bug perhaps? Why the different transport I wonder?