AmbiDecoder way too quiet?

I am setting up an Ambisonics session and I found out the Ambidecoder panner makes my tracks quite quiet.
I just created a stereo and 1OA tracks to assign them to a 3OA group, using Ambidecoder panner.
I did duplicates 30A tracks of the same, using IEM Stereo encoder and Harpex as decoding plugins.
The ones with Ambidecoder, sound around 9dB quieter.
Is there something I am missing or is it a bug?
Thank you.

it’s no bug… it just works like that…

Is there any specific reasons?
Any other formats (Stereo, Surround, Spatial Sound) sound properly, but when the Ambidecoder is used, it sounds way quieter. I think is a bug, or a bad engineering choice.

You might consider the dearVR AMBI MICRO free plugin instead of the Nuendo built-in ‘Ambidecoder’. In my experience with the Dolby Atmos setup, it is close if not totally matching the loudness.

I have DearVR, the proper one, I never use. I prefer Harpex.
I was trying to set up an exchange session with someone who do not have and cannot afford those plugins and use the factory ones made sense, until I found out the glitch.

Strangely enough, I tried to install also the AmbiMicro and now the volume also with Ambidecoder sound correct.
I just did a test with three tracks, using Ambidecoder, Ambimicro, and Harpex and now they all sound at the same level.