Target power not working with Van Rysel Home trainer

I recently bought a Van Rysel D900 Home Trainer and connected it to my Edge 530. The connection is working : I have my power on the screen and I can change the slope or the resistance from the computer. However the target power mode is not working. I created a workout to show that, I think that the problem is pretty clear on the image I attatched : at each step the resistance is reacting but it then drops to 0% (I kept a steady cadence during the whole workout). Does anyone have the same issue or know how to fix that ? The target power mode is (almost) working with Kinomap so the problem most likely comes from the bike computer and not the Home Trainer.