I am trying to stockpile soil. I removed a stockpile of planks from the spot I wanted to pile it and got the message "The ground is not flat enough." My survey shows a wide stretch of nice green dots showing all the same height of ground. Not sure how it could possibly have been flat enough for the planks but now not flat enough for the soil.
The terrain is Hardsteppe and I am using Ardennes client.
I am stacking the soil and the planks somewhere else, so this is not a game breaking bug.