then your miss timing your f3 you have a good 3 frame window to stop kung lao spin if thats what your refering to, frames are really fast there are 60 of them in a second so being just frame on cage is really hard but also works for the opponent as well, except if your a robot, then you hit everything to the frame and win at life. i would practice just doing f3's one after the other and find how fast you can get on to come out and figure out the time after each of your strings so you can get maximum speed from all your strings, this is probably the most important aspect of cage and his frame traps, if your off by a split second it means life or death