Creating a disconnect message to send through MRF

I'm working through a MRF setup and one of the cases I'm trying to implement is sending a disconnect message down to the pool members when a connection disconnects from the vhost.

There are similar connect and data messages which are sent to pool members when a client connects or sends data to the vhost - this is working fine.

When trying to send the message through MRF, during CLIENT_CLOSED, seems to drop the message with the following logged in ltm;

 Pending rule (null)  aborted for 1.2.3.6:54127 -> 1.2.6.5:33200

The message is created in the CLIENT_CLOSED event as;

 GENERICMESSAGE::message create "DISCONNECTED:$my_host" my_dest

As a workaround to it not finishing processing the irule for the message, I tried using a sideband connection and send in the message that way to a separate vhost (for different irule setup, linked to the same MRF router). This mostly works, except it has some strange side effects at the moment.

Anyone know how to get a message to pass through from a CLIENT_CLOSED event? or have the sideband connection work without affecting other connections?