So official statement goes as this:
"Sea water entered two of the four bearings that connect the port and starboard electrical motors to the drive shafts – in prevention both propeller shafts were locked, forcing tugs to help Zumwalt complete its transit. According to USNI, a service official confirmed this latest problem is similar to one that stopped the ship in September – in that case, the Navy said sailors found "a seawater leak in the propulsion motor drive lube oil auxiliary system for one of the ship's shafts."
"Sea water entered two of the four bearings that connect the port and starboard electrical motors to the drive shafts – in prevention both propeller shafts were locked, forcing tugs to help Zumwalt complete its transit. According to USNI, a service official confirmed this latest problem is similar to one that stopped the ship in September – in that case, the Navy said sailors found "a seawater leak in the propulsion motor drive lube oil auxiliary system for one of the ship's shafts."