Activating MAVLink 2 SIGNING on specific telemetry ports

Hello guys.

I am trying to use MAVLink 2 SIGNING on my drone, which also has a companion computer.

I am using PIXHAWK CUBE BLACK, with 4.0.5 firmware. I have 2 telecommunication devices connected to serial ports 1 & 2 (MAVLink 2), and a companion computer connected to serial port 4 (MAVLink 1).

Right now, when I activate SIGNING on serial1 and serial2 ports, companion computer (Serial port4), stops communicating with the PIXHAWK.

I want to apply the authenkey only to serial1 and serial2 telemetry ports, with the PIXHAWK still communicating with the companion computer, which I want to leave without authenkey.

Is it possible to configure it this way?

Thanks ahead.