I've been having a problem with the Falmer. The first time I saw them in my new save they just stood there and I think they were bugged. I thought it might have been a simple bug caused in Darkwater Pass but then I tried to do the Aetherium Wars quest. There they were again inanimate they were snarling and I heard them trying to attack but again they just simply stood there. Some of them even appeared in the floor face down.

Any thoughts as to why this happens ?

Have you any mod's ????

and

Have you installed the Unofficial Skyrim patch and the Un. Dawnguard patch as well ???