Moodle v.3.5.3+ (Build: 20181128); Themes in use: Fordson and Clean (for mobile); HTML Editor/Plugin: Atto (2018051401)
Recently upgraded to above build and some drop downs on menu's are behaving oddly re: they don't work as in clicking the button (any of the top navbar navigation buttons as well as buttons within certain pages, for example, trying to Edit a student's submission, extend assignment submission deadline in a course, etc.) do not work. There is either no activity as in nothing happens (no drop downs appear) or the page just seems to refresh or jump to the top of the page). It happens for some but not all pages. We did a test migration first on our test server and all is well no problems.
I have checked the plugin and theme settings/versions and they are the same. I mention this because I read of a bug in Boost + Atto whereby drop down menu's were not displaying as they were unable to work with a '#" in the URL (which is the case for let's say our grading page where teachers need to click the "Edit" button to access a list of options - extend, lock, etc.) but the patch is over 2-years old and I don't think it's wise to apply as test server works fine.
It seems the browser is not happy - error on page attached as image - and have tested on different browsers. Any ideas from anyone who has experienced something similar?