Line appearing across all window under tabs after Chrome update

[Hannah S.]

First thing, thank you so much for your work, I really enjoy your themes.
I've been using the 'Midnight White' theme for a few years now, but today after updating Chrome, a line now appears across the whole page (pointed to by the red arrows in the following):

This line has never shown up before, and is unsettling since I enjoy the minimalism of this theme, and the highlighting of the active tab only. This is especially irritating when working with grouped tabs:

It seems messy, and lacks its' usual simplicity , I'd love to know how to fix this.

Kind regards,

Hannah

[Hannah L]

Pictures, since they seem to not have been properly attached:
Picture 1:

Picture 2:

[Browservery Support]

Please see: https://bit.ly/3YLfLOb