haxx Can you try to disable 3rd party extensions one by one to troubleshoot as the same functionality works fine for me on local install with JA Fit
Also, On turning on error reporting to maximum, Could see error relative to System - Joomlatools Framework . Ref: Screenshot and another error relative to specific file of JA Masthead for which I have reported the same to JA Dev. Team on simultaneous basis as the error has started to appear with Joomla! 3.8.10 Stable update as being seen here for other extensions too
Will revert back as I get update on the same 🙂