Safari 12.1

       Startup in Safe Mode.    https://support.apple.com/en-us/HT201262

       Launch Safari to test.

       Restart normally by clicking the “Restart” button at the bottom.

       Turn off extensions and test.

       https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac

Try going to Safari/Preferences/Privacy and uncheck Prevent cross-site tracking to see if that makes a difference.