Integration with Koch Ecoos intercom not working

I recently bought a Nuki Opener and tried to connect it with our apartment intercom: Koch Ecoos (or IG75.1000). This device is listed as supported by the documentation and the setup app, but in practice it was impossible for me to set it up.

This is the original wiring for my intercom:

After following up the setup instructions this is the final wiring:

This is connected to the bus entries, and when configuring it the intercom requires that the speaker button is press before open, but during the setup is it asked to press the button, but the Opener does not detect it and returns the following page:

I tried both variants of the bus cables but neither option works (the alternative one makes the intercom device unresponsive due to polarity not matching). The connection seems to be correct given the Koch’s schematics

This problem does not seem to be unique (other forum entry. Is there any option to collect logs or messages that the Nuki Opener device is collecting and send it back to Nuki so it can be debug and fixed this error? I would be happy to help on having this issue fix. If more information about my device is required don’t hesitate to contact me through email.

Our intercom seems to be quite old (from before 2010). Could it be that the Nuki implementation is based on a newer version of the Koch’s TC:Bus protocol.