Gun wont fire when aiming at moving target

Ok here is the problem. My gun wont fire when I am aiming at a moving target. I tested it with my little brother. When he was moving the gun wont fire. When he stood still the gun fired. The gun only fires on objects that are still. I suspect this has something to do with my sanity checks but I dont know what. I already changed max distance from 4 to 10.(Distance of how far client ray hit can be from server ray hit)
It still doesnt work. Can someone help me?

Video: Roblox gun test. - Album on Imgur