Are there any publicly available sites where you’ve seen the issue that you’d be able to share?
If not, can you open the Firefox web console (screenshot: how to get there, what to look for), and see if you have any orange or black X’s?
The console will normally output lots of information. I’ve filtered it down to just example errors in the screenshot. If there’s not an “x”, it just informational; not like a cause of problems.
Could you possibly be running any plugins or themes that are modifying stock WordPress script behavior? For example, javascript or CSS minifiers, jQuery replacements, etc? Since you’re on a localhost install, a quick way to test for conflicts is to disable all other plugins and switch to one of the TwentyXXX themes. Alternatively, could you provide a list of plugins you’re running, as well as the theme?