A change made on the 9th of September was causing intermittent SQL transaction failures. That was fixed today and the servers restarted to insure everybody's data was in sync.
The transaction failures caused several new ship designs to not be saved into the database.
Fifteen ships existed in the game universe that had no ship designs. They were manufactured while their design was valid but, when the design failed to get saved, they became invalid when the servers restarted, or when they traveled to another server.
I deleted those ships as there was no way to repair them. No avatars were stuck aboard any of them but three of them had officers aboard them. Those officers are free now.
FWIW, this was not triggered by any specific design. The problem was triggered merely by using the on-line designer.