i just got a new guitar w/ a floyd rose on it, and i am new to these. well, heres my problem: when i tune the guitar, i undo the lock at the top of the neck and tune, and put the lock back on, and do this for the rest of the strings. the problem is when i go back, the string is out of tune by around 1/2 step lower usually. i do it over and over but it keeps happening. i have tried tuning 1/2 step higher, and stretching the strings, but nothing is working. any suggestions?