C21 bug: Unable to save updates to existing CustomTool Tabs

I have found I am unable to "save" updates to existing Custom Tool Tabs when saving Workspaces. All changes or tool additions and deletions from pre-existing custom tool tabs are are lost or reverted during save. To solve the issue, I had to delete my existing Custom Tool Tabs and recreate them so that changes could be saved.

For more information, I use Custom Tool Tabs for my customised workflows and after updating and familiarising myself with C21, I tried repeatedly to add new tools and reconfigure my "custom" tool tabs. But each time I tried to save the new workspace, all changes to to the custom tool tabs were lost. The custom tool tabs just revert to original or preexisting configuration. 

In the end, I did solve my problem, but having to delete and recreate my custom tool tabs to be able to update them is a frustrating, time consuming and unnecessary hinderance.