In case anyone out there is still battling this bug:
I tried all of the above and
But I did eventually find this solution at the SplashData website:
If you get an error mentioning SplashID Safe when you run Safari on your Mac, this may be due to an incompatible version of the SIMBL plugin that was installed by an earlier version to support the SplashID plugin for Safari.
Please download and run this uninstaller script to remove it:
After you run it, launch SplashID and login. It should clear up the issue.
The script removes the following:
This did the job on my machine.