1. Include any SVG as a repeating background image 2. Zoom in or out 3. Look very closely. There is, at some zoom levels, a vertical line between every repeat. See https://www.heropatterns.com/ or any website that uses a repeating SVG background and zoom in or out to view this issue.
More info: https://stackoverflow.com/questions/56309871/svg-as-a-css-background-is-there-any-way-to-repeat-x-with-no-space-in-between
Created attachment 370732 [details] Screenshot plus an edited, zoomed in version, showing the problem.
Here is a codepen displaying the problem with a higher contrast SVG to use for testing: https://codepen.io/TelFiRE/pen/gJzqaG
<rdar://problem/96254825>
Created attachment 466562 [details] WebKit ToT (zoomed in) from Comment 03 test case