I was also having problems with ent_fixnormals when I started using it for runtime edited models (even terrains).

ent_fixnormals(entity*,frame);

I also had no idea what to put in the frame parameter for un-animated entities. i tried with NULL, tried with 0, and tried with 1... always getting no result.

So I started using an entity propety: ".frame"
i dont set .frame anywhere, it sets itself.
so now whenever I use something like ent_fixnormals i always do:
ent_fixnormals(entity,entity.frame);

I am also a noob when it comes to normals, this is the first time I do anything with them.

I don't use .frame because I know what I'm doing. I actually use .frame because I have abolutely no idea what I am doing and don't know what value to put in there for un-animated entities, so I let engine decide for me.
Even when using real terrains that cannot be animated i have to use this entity.frame thing, but I honestly have no idea why...

As Socrates said: "the more you learn the more you realize how little you know"
(this frase is becoming more and more evident to me when learning to program new stuff for videogames. I might even set it as my signature, lol!)