@burnout426 Thanks for the reply. It doesn't happen each time I highlight something (thankfully), and usually it happens when I quickly highlight different parts of a text, but it is so unpredictable that sometimes it happens right away. I now tried to reproduce it to no avail, but it still happens at least once or twice during my normal browser usage (I tend to highlight a bit more than the average user, I assume, especially when reading).
And when it happens, it freezes right away, so the browser gets stuck with "Search | Copy" bar on the highlighted text (My Flow is disabled on my browser). The buttons, as with the rest of the browser become completely unresponsive until I perform an Alt-Tab.