Cover story. Some game’s afoot.
Normally, I am skeptical of that kind of speculation, but I think you might be right in this case. It is impossible that this ship would not have the parts and skills onboard to fix a simple galley fridge. As other posters have pointed out, the ship is loaded with cooling and HVAC gear and similar technology. They are going back for something else and the admiralty does not want the details made public.