I can't yet see the images (they should be approved and appear later) but this sounds like a bug with the Hub 4 to me.
I can do what you are trying with my third party (D Link) router, though I have to use the 'Virtual Server' option in the port forwarding menu to do so (to map an external port to a different internal port). My D Link router lets me do what you are proposing and successfully saves/implements both those rules.
I can also do it with a BT Home Hub that I just tried.
I've seen a lot of issues with port forwarding reported with the Hub 4. I've no idea if the Hub 5 is any better (I doubt it).
I suggest you get your own third party router and use the hub in modem mode.
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I know a bit about Wi-Fi, Telecoms, and TV as I used to do it for a living but I'm not perfect so don't beat me up... If you make things you make mistakes!