To reproduce this, I deleted a stored upgrade configuration, and then saved a new one with the same name as the deleted one.
Notice:
Error while running event on_gui_click (ID 1)
Gui element with name upgrade-planner-storage-entry-4 already present in the parent element.
stack traceback:
upgrade-planner/control.lua:459: in function 'gui_store'
upgrade-planner/control.lua:557: in function <upgrade-planner/control.lua:545>
