Router Zyxel EX3301-T0 static IP address for wired device

I did assign a static IP address 192.168.1.3 for a device, with a known MAC address,
which was connected by wire to the router.
That was done via "Home networking" → "Static DHCP".
However, in the page "System" → "ARP Table", the MAC address was bound to a
different IP address. So the static binding did not work.

I also tried to reboot the router, and the device, and even tried to decrease the DHCP
lease time to 2 minutes. But nothing of that helped. The device persistently got the same
IP address, and not the one I had defined.

Interesting though, is that static IP addresses for wireless devices work!

Do you know a solution to this problem with wired devices?