Hi, thanks for reporting this! We updated the buttons’ selectability on Monday, and it looks like it wasn’t tested to work correctly in all cases. We’ll revert the change as quickly as possible. EDIT: It’s reverted now. In the meantime, using Part.Shape=Wedge instead of Wedge or using right click → Union should work. For self-unioning, right-click is probably the fastest way.
Sorry for the inconvenience!