as I see there is a problem also with common decal shadows when mirrorwater and terraintex are applied for water and ground terrains respectively.
you can check it in my preload_mode-animation problem-demo if comment lines 168 (my.shadow = ent_unitshadow_rot;), 230 (preload_mode = 3+4+8;), and 240 (shadow_stencil = 1;) linked at another thread.