Sorry, I could not keep the plugin and had to deactivate it. What I realized was, that all of my forms entered with a shortcode on the pages had suddenly frames around them. Also my widgets had frames around them. It did not block the functionality of the other plugins or widgets, but it drew frames around forms and bars. I think this is due to not specific enough css codes.
I am using Edin theme and mostly shortcodes from the plugin WP Members were affected.