Sidebars Pro not working properly anymore

Hi, the Custom Sidebars Plugin stopped working in my page.
Two problems have appeared:
- When trying to create a new Custom Sidebar, in the Popup there is already a message below the input field for the name, even if nothing has been entered yet. It says "This name is already in use".
That makes it impossible to create a new sidebar.

- When opening the options of a widget, the following error code appears instead of the options normally inserted by the Plugin:

Warning: Missing argument 2 for apply_filters(), called in [...]custom-sidebars/inc/class-custom-sidebars-visibility.php on line 531 and defined in [...]wp-includes/plugin.php on line 177

I use the latest versions of WP and Plugin, tried to reinstall the plugin, disabled all other plugins, but nothing helped.

Thank you for looking into that!