[{HVY-E}Jinxx]

It's supposed to be moving to the original position, but the cross should be staying on the target.
If the cross is moving away from the target, you have your speed/alt wrong. More than likely it's your speed.
You must enter TAS (true airspeed) into the bomb site, not indicated.

There are several tutorials out there to teach you how to do this correctly, but I highly recommend using the manual method rather than the auto method.

Check out {HVY} Iron's bomb site manual.