When truck 81-9022 arrived Aeroklas, driver contact security guard and weight scale his truck after that he park the truck at old factory to do document process. During parking, he using wheel stopper for full truck. Then he go to factory 3 with Aeroklas's staff to unload the product.(Distance from old factory and factory 3 around 2 kms.)After finished unload a factory 3, he back to old factory to do document process and during parking, he didn't to use wheel stopper for empty truck (Only turn off engine, hand brake, take off the key).When he out of Aeroklas's office, he saw truck slice/slow moving then he told to other people help to stop his truck. Truck move from original drop to new drop around 9-10 meters.