This just started happening on a site. Using mobile first breakpoints, when I’m creating a class, any classes I create, will not work below 991px (one of my breakpoints). Even when I create any styles at the base mobile breakpoint, when inspecting the site, it will have the media query somehow injected into it. When I go to check the source code, no such media query exists. Is this a browser bug? Tried both Chrome and Edge, as well as Firefox.
This was happening on newly created classes, but I just saw it happening to older ones now, and going to an old revision didn’t help.
So I pulled out an 3 day backup of the site. Installed that onto a clone installation. It works fine. Export that block as a template, install it onto the current site, and it breaks again.