From g.co/reportbadreflow:

https://boards.4chan.org/wg/

" - Make sure 'image expansion' in site settings is enabled.
 - Click and expand an image with size that is taller than the browser viewport.
 - Scroll down until the bottom of the expanded image is about 1/10 of the way up the viewport, leaving a small gap at the bottom.
 - Close the expanded image.

Originally,  the site handles the reflow by positioning the unexpanded image at the top of the viewport. Now, when undesirable scroll anchoring is triggered, the image will be found peeking out of the bottom instead."	

Frequently