Port Forwarding V7610 not working properly

My client has just recently moved to NBN from DSL. Telstra have installed the new shiny V7610 (a rebadged Netgear) modem / router.

Configured 3 port forwards to allow remote desktop access to the internal devices from the internet

The primary rule external 3389 to internal 3389 works fine

External ports 3391 and 3392 mapped internally to 3389 to the respective devices fail

As per below RDP_DEB works, RDP_JO and RDP_SRV do not. IP's are correct, was woeking perfectly on old modem before we went NBN

# Service Name External Start Port External End Port Internal Start Port Internal End Port Internal IP address 1 iC54285 54285 54285 16402 16402 192.168.16.5 2 RDP_DEB 3389 3389 3389 3389 192.168.16.100 3 iC53199 53199 53199 16402 16402 192.168.16.104 4 RDP_JO 3392 3392 3389 3389 192.168.16.101 5 RDP_SRV 3391 3391 3389 3389 192.168.16.2