I have shipped my unit in Germany and this is the feedback of the techical team :
"Hello Sebastien, I have checked the device, and luckily, there is nothing wrong with the device but with the software.
As it turns out, this is a software-based problem. The activated Pad (Main out -12dB) Function in the output menu is causing that problem. This problem is not present when the function is not used.
So, this is a software-based issue, and we can send the device back to you soon.
Sorry for the inconvenience; this was a strange case, but thank you for bringing our attention to that issue."
So there's a Software bug which been certainly solved in the next Release