Any hotbar slot triggers it, no matter what is in it (empty ones do it too), only happens for the ship directly docked to the shipyard core anchorMostly fixed.
It's something only the shipyard core anchor showsYou can dock to a shipyard anchor with a **rail docker** or by using a **ship core** docking beam.
The same should apply for un-docking and in this case only a **rail docker** will do that, any other rail block is finethe **ship core** beam does nothing so that needs to be fixed.