After taking the device out of the box I noticed a weird "rattling" noise coming from the housing (inside). It turned out that one of the two nuts was missing which fixes the transformer to the bottom plate. Because of that, during shipping some connectors were simply disconnected from the PCBs and the other nut got very loose as well. After fixing these issues, the device is working as described.
Good build quality air flow station. fast heating. the air flow is powerful. nice tool.