Great, thank you for this first advice.
But, I've seen the 'Translucency' menu item, have disabled it and I don't see any difference
I have all my processes with Translucency mode ON and no problem. I see correctly the difference when I activate/deactivate it.
Do I need to restart Pixinsight ? I don't think so.
For this two particular frames, it's far more translucent and I hope you are able to see it on my capture screen