My mechanical worm-gear slides have a manual crank mode, but you have to remove a pin first. The motor has a brake on it which locks the shaft when there is no 12V applied to it to keep the slide from creeping out due to vibration. For this reason, you have to decouple the motor shaft from the rest of the assembly before going to manual crank mode.
I once had the brake fail and refuse to let go. If the slides haven't been moved in 5 years and won't go when you push the button, check to see if you have the brake, which might have seized up.
Steve
