Do you see your feet come down onto the beam when you step down out of a handstand? If not--that's the key problem right there, and it's an easy fix--just takes time and numbers. Try doing tons of handstands on the floor and low beam and watch your feet come back down to the beam. Then, once you're confident doing that try looking for them on your backhandsrping. Remember, your bhs is a handstand step down, except you go into it backwards and with a jump. Some people are able to register in their brain that they're seeing their feet rather easily, and some people have to think about it a little harder. Try not to worry about it too much--just keep practicing and building your confidence--it'll come.