DHCP Relay is broken in ER8411(UN)_V1_1.3.6 Build 20251028 when we shutdown the device

Model: ER8411  

Hardware Version: V1

Firmware Version: ER8411(UN)_V1_1.3.6 Build 20251028

The DHCP Relay functionality is broken in the ER8411(UN)_V1_1.3.6 Build 20251028  firmware. The router forwards DHCP datagrams from configured VLANS to the DHCP server, but it does not forward DHCP replies to the client(s).

topology:

P.S.

The router managed in the standalone mode.

Tests performed next:
Relay reconfiguration = done. Test: relay functional.
Router reboot via the web interface = done. Test = relay no longer works.
Disabling and then re-enabling the relay = no effect.
Changing the relay address to a new secondary DHCP server => DHCP relay works again.
After 3 minutes, switching back to the primary DHCP server relay = relay works.

We repeated the tests several times and were able to simulate the failure.

In summary:
As soon as there is a reboot (manual or due to a power outage), the relay stops working. To make it work, you need to modify the DHCP configuration on the LAN interface. Either by modifying the DHCP relay or enabling the DHCP server. Then re-configure the router (wait 2-3 minutes between each modification).