Bug: Trench warfare: using trenches for your advantage

[AMX]

*tries*
It's not in the scenario editor, it's in the deployment phase of a generated battle.
Building a trench changes the terrain to "clear" without changing the terrain graphic, clicking the "remove trench" button removes the trench without restoring the original terrain.
Not sure if it happens with all terrain types, but it does with "Rough", "Field" and "Tall grass"
Also happens in WW2.