Ruins Clutter Improved changes the UV Map for the imperial portcullises, but Underground - a dungeon texture overhaul overwrites its textures with ones which expect the vanilla UV Map.
Delete the following files from Underground - a dungeon texture overhaul
\textures\dungeons\imperial\impwooddoorsingle01.dds\textures\dungeons\imperial\impwooddoorsingle01_n.dds
Ruins Clutter Improved changes the UV Map for the imperial portcullises, but Underground - a dungeon texture overhaul overwrites its textures with ones which expect the vanilla UV Map. Delete the following files from Underground - a dungeon texture overhaul
\textures\dungeons\imperial\impwooddoorsingle01.dds
\textures\dungeons\imperial\impwooddoorsingle01_n.dds