Do not dig behind retaining walls

Make sure that the excavators do not dig behind the retaining wall. For if you place the walls one after the other, the excavator begins to dig the ground on the other side through a 5-meter wall, which is why everything collapses.

I agree although this has been suggested elsewhere many times.

Like-wise, don't dump behind retaining walls. I realized too late that my walls did not sit on the edge between two tiles so when I dumped "above" them the material went through it onto my road below.