The ultimate way to uncock crossbow is shooting an arrow into the soil in a safe area. There are three ways to uncock the crossbow:
Using a Discharge Bolts
In this method, the discharge target is used to unload the bow. Discharge targets are small archery targets that are portable and have a thick material. It will stop a bolt at close range. Discharge targets are easy to use.
Using an Unloading Bolt
Discharge bolts are specially made for uncocking a crossbow safely. These are heavy duty arrows. The technique is the same, though you have to shoot a crossbow in a safe area and at last some cranking mechanism offer.
They can work well. However, they need soft ground, and there is a chance of them burying themselves deep into the dirt or worse skipping off the field.