screen replaced and now it doesnt respond correctly

hi, i followed the directions on replacing the front screen and everything went well. i put it all back together and turned it on. then noticed that when typing sometimes the letters do not come out as i type and sometimes it punches 3-4 extra letters, this appears to be rather random, sometimes it does it and sometimes it doesnt. my question is have you come across this and is it a simple fix or something alot more complex? many thanks for your time,

Wayne

the screen works fine when I took off the screen protector form it