I only noticed this last night, as I have not used the toolbox on this particular project for some time. Suddenly, all my Telerik controls, previously on their own tab, were missing, and this mysterious, empty tab #13119 was there. I added a new tab for Telerik and added all the controls, but the Telerik tab remained invisible, although the controls are still ticked to indicate that they are in the toolbox.
Share
I get this now and again. Try right clicking the Toolbox and select ‘Reset Toolbox’