The U.S. Navy experienced another setback for its controversial Littoral Combat Ship program with the futuristic-looking USS Coronado experiencing an “engineering casualty” today en route to the Western Pacific after participating in Rim of the Pacific war games in Hawaii.

“The crew took precautionary measures, and the ship is currently returning to Pearl Harbor to determine the extent of the problem and conduct repairs,” the Navy said in a release.

The 421-foot all-aluminum trimaran, which left Pearl Harbor on Friday, is operating under its own power and and is being escorted back by the replenishment oiler USNS Henry J. Kaiser.

The extent of repairs and any operational impact “is unknown at this time,” the Navy said.

The Navy is building two Littoral Combat Ship variants, and the Coronado’s deployment represents the first of its type to the Western Pacific and Singapore.

“Last night’s problem is the fourth issue in the last year” involving Littoral Combat Ships, Chief of Naval Operations Adm. John Richardson said in a release. “Some of these were caused by personnel, and some were due to design and engineering. These issues are all receiving our full and immediate attention, both individually and in the aggregate.”

During RIMPAC, the San Diego-based Coronado fired the first Harpoon missile from a Littoral Combat Ship in a “sink exercise” involving the retired frigate USS Thach.

The Navy originally wanted 52 of the warships, which were touted for their speed and shallow draft for operations in near-shore environments against pirates, mines and diesel submarines. With the rise of China, however, concerns were raised about the ships’ armor and lethality, and the Pentagon reduced the total to 40, which includes current Littoral Combat Ships and an upgraded version being referred to as a “frigate.”

The Coronado was fitted for the deployment beyond Hawaii with additional Harpoons, which have the capability of destroying enemy ships 100 miles away, the Navy said.

The Navy is seeking to arm all of its Littoral Combat Ships with over-the-horizon missiles to increase the ship’s ability to fight at greater distances as nations such as China and Russia continue to refine their own long-range anti-ship missiles.

Two shipyards are building an equal number of two different versions of the Littoral Combat Ship. Lockheed Martin is constructing the Freedom variant with a steel monohull and aluminum superstructure, while Austal USA is building the all-aluminum trimaran Independence version.

Breakdowns in the past 12 months have included:

>> The Navy’s first Littoral Combat Ship, USS Freedom, experienced a July 11 casualty to one of the ship’s main propulsion diesel engines caused by a leak from an attached seawater pump mechanical seal.

>> The USS Fort Worth experienced damage to the ship’s combining gears on Jan. 12 while in Singapore. The ship’s commander, Cmdr. Michael Atwell, was relieved of command, the Navy said. The ship, which had been in the Western Pacific since November of 2014, departed Changi Naval Base in Singapore on Aug. 22 headed home to San Diego.

>> The USS Milwaukee was about 40 nautical miles off the coast of Norfolk, Va., in December when it experienced a loss of propulsion. Metallic particles were discovered in the port combining gear filter system.

“Given the engineering casualties on USS Freedom and USS Fort Worth, I believe improvements in engineering oversight and training are necessary,” Vice Adm. Tom Rowden, commander of Naval Surface Forces, said in a release this week.

Singapore’s Ministry of Defense said the first Littoral Combat Ship deployed to the country in late 2013, with the possibility of up to four of the U.S. ships to be rotationally deployed to the region in the future.