then the microcontroller keeps reseting everytime I try to move the servo.
Simply changing the crystal, or the timing, won't cause a reset.
When a servo is commanded to move, it'll cause a power drain. If the power drain is too high for your battery, voltage drops, and it'll cause a mcu reset. A servo PWM, if programmed to be too fast, can greatly increase the power a servo requires . . . your servo will vibrate a lot, overheat, and burn out.
In other words, it sounds like a power supply issue with your circuit