UNITED NEWS INTERNATIONAL (UNI) — The U.S. Navy’s new $13 billion carrier suffered another propulsion failure at sea, raising questions about the reliability of the Navy’s newest class of aircraft carriers.

According to a May 8 report by Bloomberg, the first-in-class USS Gerald R. Ford suffered a previously unreported propulsion problem in January.

The issue forced the carrier to return to port early from sea trials.

According to Bloomberg, the issue has yet to be resolved.

In April 2017, the Ford suffered a similar issue with its main thrust bearing.

Shipbuilder Huntington Ingalls said that the issues were detected during what’s known as a shakedown period, in which they can test the ship’s systems and work out any bugs.

Officials said the ship will be ready for initial combat duty in 2022.

The Ford is the most expensive warship in history, costing nearly $13 billion in construction and another $5 billion in research and development.