How to reproduce :

• Create a validator to easily generate errors on content modification (only server side eroors)
• Add this custom validtor to on content type's attribute
• Open the solr search tool
  • Select your content type, and add the attribute in columns
• Modify the attribute's value in order to generate the error
• Save
  • Some ribbon's buttons have the spinner => OK
  • The error dialog box appears => OK
• Click on ok button
  • The spinners do not disappear => KO