Task items are not appearing on the K2 Worklist until many minutes later. It appears MSMQ takes longer than normal to process messages in its queue.
This was a result of a huge amount of data in the Eventbus table in the database.
We had to 'clear out' the redundant data from the Eventbus table in the K2 database to reduce the MSMQ overhead.
Please note if you are a blackpearl(on-premise) customer you will need to contact Support for assistance with this procedure.
A TFS item for enhancement to ensure that the data in the EventBus table is monitored for efficiency has been logged and will be implemented in a future release.