Screen flicker when viewing at certain angle

Hi everyone, I am new to the forum as well as unreal engine.

I am creating an AR game and find flickers when viewing at certain angles.
flicker

I suspect it might be related to lighting and CSM shadow.
When the “maximum number of CSM cascades to render” increases, the problem occurs less.
When the lighting intensity changed with the environment, the problem occurs more frequently.

I have tried to turn off the shadow casting on the lights and meshes, but the issues still persisted.

I would be glad if someone could point me in the right direction.

Thanks a lot,
Mark