Replying to K-feds on short rails

so today I got a new rail about 3 feet tall x 8 feet long, and I simply cannot k-fed on it, and it's pissing me off. I can front 2 out, blind 2 out, front 4 out, and even front 6 out off of the same rail with ease, but can't manage to k-fed for some reason. is my rail just too short to k-fed on, or do I have bigger problems than faulty equipment? I can k fed fine on other rails, just not this one for some reason. thanks for letting me waste your guys time haha