Diagonal lines in exported model from Blender

[Ahmed-UPEC]

Hi there,
I'm using blender and react-three for a small project
Made my model on blender following polygun runway tutorial, but when exporting the model to my NextJS and React-Three APP
I got some weird effect on my model. After digging it I found that normal option (while exporting) causes the issue.

Can anybody help me out, maybe im doing something wrong on blender because if I download a model from internet those diagonal lines doesn't show up
Respectfully
Ahmed

[CodyJasonBennett]

This is shadow acne, you can control the shadow depth bias with <directionalLight shadow-bias={-0.001} />.