Excavator driving down into divot between dumped land and retaining wall

This excavator is driving on the angled surface between this dump zone and the conveyor wall.

unless you see it not getting out any more, this is just a visual issue and not affecting the intended function. in most instances vehicles seem to use the surface normal for their render position/orientation. so them sitting right on the edge can sometimes lead to weird visuals.

if it's not getting out any more it's a edge case of path finding where the excavator logic does not look ahead (far enough or at all) to consider where it should start digging to not dig it's (sometimes literal) own grave. intervention by the player is needed in that case (for example by resetting the excavator)