The animation stutter only happens on magos, if you're using that to view this.
As for the ending as they start, I hope you're not referring to the stand ready animations. You know that's how it works for the ranged attacks. (But most likely not, since you mentioned lots.)
Most likely, what you're referring to is a magos issue.
As you probably know, magos is the only one who doesnt automatically use the first frame of an animation as a reference for the last frame, while the rest of them (mdlvis, hive viewer, ingame) do - because that's how it works ingame it.
So it's actually much more optimized to do it this way, even if magos doesn't like it, since this is meant for warcraft not model viewer.