Severe lag with lighting!

I’m not sure how else to describe the issue, with the shadow property of light objects enabled, while being in a specific spot, facing your camera north, it decreases the fps greatly

Note, I’m looking for a genuine reason and solution to this apart from switching off the shadow property, I want to make this a graphics setting in my game so help is greatly appreciated

the video link has better resolution because of the length of the footage so you can see the fps clearly

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