I know you don't mean to be offensive, but please don't assume im a idiot!
My cap is not even close i still have over 6k of free space it is the wall construction not triggering right and it keeps re appearing even though the walls are complete. Some times if i stay logged on long enough and i keep disabling auto wall construct it will disappear for the duration of the game. but when i log back on it strikes again.
I have played with it enough to find out that it will consume both gold and stone like walls are being constructed while im logged off and i have have alot of gold it may last until i log back on but of-course at a lower amount then when i left. So i believe it to be the auto wall trigger that is not functioning properly and is consuming my resources.