Why does my touch stop working when the phone screen faces down?

So after replacing the phone screen I noticed that everything would work fine until I would make the phone screen face down towards the grounr. Once I do that touches would no longer register and I would have to power off and on the phone to get it to work again. As long as I keep the screen facing upwards it will work. Is the screen defective or is there something specific that I could have done wrong in the repair process?