Hello Alberto
After a lot of experiments with PPV, console commands (24 unsuccessful renders haha) I finally found a solution :
First, I replaced my DefaultEngine.ini with a UE5 default project file (the one I was using came from Rural Australia demo), then I changed my PPV and MRQ settings according to William’ s videos (lumen explained and MRQ settings part01)
But I also added theses commands :
r.Lumen.ScreenProbeGather.ScreenTraces 0
r.Lumen.Reflections.ScreenTraces 0
It just solved the problem, no more flickering shadows !
Huge thanks to William and to you Alberto, for your more than welcome help
I can now move to the metal reflections 