When putting com.liferay.portal.servlet.filters.language.LanguageFilter=false
we noticed JS errors in browsers of type "Uncaught TypeError: Cannot read property 'RULES' of undefined".
This issue is claimed to be fixed in
LPS-6323 but it seems still to happen.
For example you can go to Control panel and try to change your password while watching the JS console.
The result is that password can't be changed and there is no error, except in the browser console.
Similarly you can't change site settings, e.g. update site urls.