2 issues:
1. If you press the "undock" button and undock a constructed or a docked ship from a shipyard, you won't be able to re-dock that ship to the same shipyard.
2. When pressing the "undock" button, you'll always get the error message "no ship docked!" but it undocks fine anyway.
This is what you get: {F1536}
How to reproduce:
# dock a ship to a shipyard/construct a design
# undock it by pressing the "undock" button (and notice that you get the error message "no ship docked!")
# try to re-dock that ship to the same shipyard
# you can't and it will give you the message that it does not fit which is not true.