I like that version of the lore but I added my own. Enterprise A is actually the Yorktown… but why was the Yorktown available you may ask? I mean it would have had a captain and crew right?

Well it was one of the ships that attempted to intercept the whale probe during Star Trek III The Journey Home and had its systems soo badly scrambled that it lost all power and was running life support on batteries. (Which happened in the movie and was a transmission received by Earth, it is even mentioned that they were trying to assemble solar sails to attempt to make it to a habitable planet.)

Well the fearless crew of the Yorktown didn’t make it and the entire crew suffocated or froze in the cold blackness of space…

Starfleet isn’t so big that it can waste a starship even if it’s full of frozen dead people. So they spaced the bodies, cleaned it up and stuck Kirk with a malfunctioning potentially haunted ship as a kind of punishment.

This explains why nothing worked on the Enterprise A in Star Trek IV as its systems were still pretty scrambled from the Whale probe and was haunted by the long dead crew of the Yorktown…