Steps to reproduce

1. Define a rich text with annotation:

   <cms:metadata name="richTextWithAnnotations" type="rich-text">
       <cms:label i18n="false">My rich text with annotations</cms:label>
       <cms:description i18n="false">My rich text with annotations</cms:description>
       <cms:annotations>
           <cms:annotation name="myAnnotation">
               <cms:label i18n="false">mine</cms:label>
               <cms:description i18n="false">My Annotation</cms:description>
           </cms:annotation>
       </cms:annotations>
   </cms:metadata>

2. Edit a content with this rich text and add an annotation on a word in the text.
3. Then try to remove it by selecting a part or the whole word and click again on the annotation.
4. The annotation is added twice.

Workaround: Open the rich text with the XML tag, and remove it manually.