Asus-merlin 384.17 on Asus RT86U, GIU does not change (in real) ports forwarding. How to fix?

[Klagio]

Hi I have an Asus RT86U with flashed 384.17 asus-wrt.

Everything works well except when I do change the port forwarding from the GUI, sometimes the command is taken and sometimes not.
BTW this happened also with previous versions.

Let me explain better how to reproduce the error:
1) I forward 443 TCP port from outside to a local LAN 192.168.1.11
2) it works fine, when I access https://mydomain.myddns.com, I get forwarded to my server/software in 192.168.1.11
3) I want to change the forward to a different internal IP address, so I go to the GUI, click the pencil for EDIT, I do change the local LAN to 192.168.22, and click save
4) the GUI shows the new modification, but in reality nothing has changed, all external communication still go to 192.168.1.11

Tried also to reboot, but the roblem persists, and is kind of erratic.

How can I solve? Perhaps not using the GUI but with terminal? Can you provide a tutorial on how to access the router in terminal and how to change port forwarding?

Or any other hint on how to make sure the correct port forwarding is done?