Port Forwarding config partially lost at every reboot RT-AC66U

[Homie]

Hi all,

I have this strange problem since upgrading my RT-AC66U to 3.0.0.4.376_3861

I have added a port forwarding rule of ports 5000, 5001 for remote accessing my Synology NAS which sits on a private IP on my LAN. And everything works great (yay!) until I reboot my router. All of a sudden, this last added port forwarding rule is lost?

It seems I need to add it manually after each reboot. This never used to be the case... Am I missing something here in making it save properly or is it in fact a new bug?

Thanks.