Geodatabase annotation feature class contains an invalid item that cannot be deleted

Description

Cause

This is a problem caused by a third-party software called ICOMAP.

Solution or Workaround

1. In ArcCatalog, right-click the annotation feature class and select Export > Geodatabase to Coverage.
   
2. Enter an output coverage and subclass name.
3. Click OK.
   
4. Right-click the new coverage annotation feature class and select Properties.
5. Click the Items tab.
   
6. Highlight the invalid item and click the Delete button.
7. Click Apply and click OK.
8. Convert the coverage annotation to geodatabase annotation using the 'Convert Coverage Annotation' tool in ArcMap. Instructions for performing this conversion can be found in the ArcGIS help under Contents tab > Geodatabases > Managing Annotation > Converting coverage and SDE 3 annotation to geodatabase annotation.