GTM showing Generic Host type Server as UP when it is actually DOWN

Hi, We have a GTM->LTM setup whereby :-

On the GTM :- - I've configured a Server as Generic Host, assigning it the VIP address of the Virtual Server on the LTM I want the traffic passed to - assigned that same VIP address to the Virtual Server tab within that Server.

So I have a Generic Host Server created with address x.x.x.x and if you click on that server, click on the VS tab, you see an entry with the same IP.

What I am seeing is that when the LTM (which is running that VIP address) is marking that VIP as being DOWN, this is not being reflected on the GTM. The Generic Host Server is still showing GREEN. I seem to be using the correct Health Monitor as when I change the monitor to something completely different, it does change to RED.

Anyone got any ideas as to what might be causing this?

Thanks.

Alan.