Port forwarding broken

Since trialling and disabling xfi, I cannot configure port forwarding on my router.

However, using the online interface, i cannot edit or delete port forwards ("we're having a problem, try again"), only add.

And now, existing port forwards have failed.  I have disabled firewall on the device that is being port forwarded to so I can ensure it's not a local issue, but the port forwards fail to work in any configuration.

How can I return the router to allow me to locally manage port forwarding?