If with "the gate has already marshaller sign", you mean the gate has a Visual Docking system so it wouldn't need a Marshaller, it's entirely normal because, if a scenery uses its own Visual docking system, GSX cannot possibly know about it. GSX can only recognize a Visual docking system if:
- It's a Visual Docking system added with GSX
OR
- It's a SODE VGDS Docking system, which requires a SODE payware extension called SODE VGDS
If the scenery uses any other method to create Visual docking systems, you must configure the parking in the GSX configuration page, to disable the Marshaller, by setting the Parking system to "None".