I haven't seen this, and it's quite difficult to diagnose from afar. At first impression, I ask if there is some browser extension that is interfering with proper rendering. And can you look at the browser in debug mode to see what's going on? We don't use Safari too much, but I know with Chrome on occasion, browser extensions have gotten in the way. And have the user try a different browser on the same machine such as Chrome to see if the behavior is the same.