ok i’ve deactivated the plugin and then replaced it with the new one and then reactivated. Now my described WYSIWYG problem is fixed. The one specific field is working again. Coolio!
p.s. @Elliot Condon you can drop and forget my mail i’ve sent to your support mail address one or two day ago about the WYSIWYG issue, your hint here already fixed it 🙂 thanks a lot!