That happened to me, too, 2-3 months ago - and has persisted.  Of course, the advice is going to be to reboot, clear the cache, etc. - but that's stock advice for any problem you'll run into. 

In my case, the issue is still there - I've had to learn to live with it.  I've rebooted and cleared cache and used other browsers and used private browsing and all that, but nothing changes. It's simply a new behavior in the software, and I doubt they'll address it.