This is SOAPUI packaging issue since 5.2.x.
Once installed, SOAPUI places some plugins under "C:\Users\<user name>.soapuios\plugin".
For SoapUI 5.2.1, there are 4 default plugins installed under this directory:
Just rename the original folder 'plugins' to 'plugins_justForPro' (or something else), so that default plugins could be forced hidden during runtime. The problem then disappears.