SenseCAP LoRaWAN Outdoor Gateway offline operation

Hi,
SenseCap gateway comes with a Chirpstack already installed, it can be accessed on a different port. You can see it here, under point 5.

I believe MQTT forwardes is not an issue, it works fine when the network has access to the Internet. When I unplug Internet cable from the switch, it doesn’t work anymore. Similar issue was described here: ChirpstackOS - as standalone with no internet

As you can see in the photos below, when I use the network without Internet access I am receiving lorawan frames, but nothing gets sent as MQTT (nothing appears in the device data tab as well)
[images here, blocked because I am a new user]

However, when I connect Internet to the network, everything starts working correctly and I am able to receive MQTT messages
[images here, blocked because I am a new user]

Forwarder config: