FW rudder doesn't get yaw input

Good morning everyone,

I am actually working with PX4 to send custom angle inputs to a FW.
Given that no offboard mode exists for FW, I created my own mode in order to give inputs directly to actuators via actuator.control.
I implemented a controller to make the FW follow angle references: roll and pitch work good, but I can’t say the same for yaw.
The actuator gets the input, but the rudder of the model (I use Gazebo + QGroundControl for simulations) doesn’t answers to it.
Is there some flags I am not setting or, more in general, something I should do to allow yaw control?
Thanks to all in advance.