As shown in the attached video, if you have a course page that's longer than than the screen, but by less than the height of the tabs, scrolling to the bottom causes the tabs to flicker between showing and hiding creating an unpleasant effect.

The video shows this on a device with our custom course format, but I have also reproduced it on http://school.demo.moodle.net with a 3.7 Moodle Desktop build.  For example, if you view the Digital Literacy course, select only the "About this course" section, and resize the window to 330x580 and scroll to the bottom, the problem occurs.