WL-Wnt100x3(-a) — Can the travel router not use WireGuard over LAN?

Hello everyone,
I have a strange problem with this travel router (without the “-a” extension).

With multiple WireGuard configurations that have worked flawlessly many times, I was able to establish WireGuard connections to the router via Wi-Fi without any issues.
However, when I use the router’s LAN port to connect to my PC, the WireGuard connection no longer works.
Is this an intentional feature of this “travel router”?

A similar router from another manufacturer allows WireGuard to be used via LAN without any problems.

How can we teach the 100x3 to run the WireGuard function over LAN as well?
I purchased the travel router at the beginning of August, but I was only able to install and test it now after entering China.

A bit of confusion regarding the firmware:
The router has WL-WNT100x3a_v25072 installed.
On your page, WL-WNT100x3_v241212 is available. It seems to me that this would be a downgrade.