Troubleshooting Safari plug-ins and Extensions
How to troubleshoot Safari third party plugins and extensions:
From the Safari menu bar click Safari > Preferences then select the Extensions tab. If there are any extensions installed, uninstall one at a time then quit and relaunch Safari to test.
If it's not an extensions issue, try troubleshooting third party plug-ins.
Back to Safari > Preferences. This time select the Security tab. Deselect: Allow plug-ins. Quit and relaunch Safari to test.
If that made a difference, instructions for troubleshooting plugins here.