This can be reproduced in both the testing and demo environments. There are two problems; (1) the Event 1 view is not resetting the view to display groups 1 to 3. (2) the label is appearing on the wrong group if groups 2 to 4 are displaying in the query tool. The problem of not being able to drop a concept into the panel labeled Anchoring Event is by design. This is because the label is technically appearing in the Group 2 panel. The Web Client prevents users from adding concepts to a panel if the previous panel does not have a concept. If you click on the left arrow to display group 1 you will be able to add an item.