Firewall/Port forwarding when limited to specific IP Adress: Firewall "forgets" that IP Adress

I am running a rsync backup from a remote WD MyCloud NAS boxe to a similar box behind my Turris Omnia. For security I limit the port forwarding of port 22 and 873 to the specific IP Adress of the remote box. See Screenshots below.
Form time to time and reproducably after reboot the firewall “forgets” the allowed IP and stops forwarding the ports altogether. After editing the rules (e.g. changeing ports and back, as in the screenshot) in LuCI it works again. (Surprisingly a /etc/init.d/firewall reload doesn’t help…)

This ist happening since a few months, quite possibly since I moved over to TurrisOS 5. Before that I didn’t have the problems. I am on TurrisOS 5.1.1 Branch HBT.

Any Tips on how I make the rule permanent?

PS: Yes I know standard ports are not the best Idea but they cant be changed in the WD Mycloud box when using the original WD Software/Webinterface.

This is apparently fixed by TurrisOS 5.1.2 Turris OS 5.1.2 is now in HBT (Testing) branch