This was driving me crazy as I couldn't see any "locked" items selected. Eventually it turned out that the checkbox for T5 under investment income was selected (copied from previous year), but this was not visible as the parent item "investment income" was unselected! So to undo this you have to select the checkbox for investment income, unselect the T5 (or whatever) and then deselect investment income again. It's almost as if they want to browbeat you into paying for a higher priced product you don't need ...
