At first I realized that the network ID doesn't work on my Exotic Industries game. The trains from network 1 yoinked items from network 2, and vice-versa.
Then I tried on vanilla, the issue still persist. Please fix it :3

Thank you

In your situation you may not have the combinator conected correctly, turned on, or may have the network misconfigured to be more inclusive than you believe. If the combinator is on, connected to the station lamp and is not emiting the configured Network ID, please provided a save game, screenshot, or something showing what is not working correctly. I'll be happy to look at it.

The mechanics of the LTN Networks is part of the LTN mod, not the LTN Combinator mod. If there is something that isn't working correctly with LTN, you'll need to report that to LTN's author.

I've re-read the LTN Manual Guide. It turns out that a Network is also connected to other Networks that has "smaller ID" than it
There's nothing wrong with the combinator. Sorry for the wrong report, and thanks for the reply!