got the same issue since a while back. Game starts out fine but after crossing a few cells, the issue reoccurs. As Gwain96 points out, the fully detailed textures ARE being loaded, but the LOD textures are not unloaded, so they overlap each other. Saving and reopening the game, fixes the issue. So simply stated the issue is that the distand LOD textures are not unloaded upon approaching the area. Also happens upon fast travel. Not sure how to explain that.