Thin line under the navbar on wider displays

Hi,
I noticed a thin line under the navabar when displayed on bigger widths (try 1300px and 1800px). Any ideas what causes it and how can I fix it?
Thanks.


https://preview.webflow.com/preview/arclight-d2f80e?utm_medium=preview_link&utm_source=designer&utm_content=arclight-d2f80e&preview=590039944bc71fd88d66090257979155&workflow=preview