Why is Mesh flickering after adding a RectLight?

Development Rendering
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1

Hello,
A mesh is flickering after adding a rect light, if I use light in a material everything is good, why can it be? there is no double mesh btw. If I turn of shadows from the light it is getting normal. But I need shadows (
Here is the video:


So, I also installed the last UE 5.4. and it looks better now but still not perfect:
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It is not flickering but static strips of shadow.
I am looking forward to hearing from you.

2

I can’t really tell what the problem is but can you try with a point light or a spot light and send me a photo of the update.