The first of 9 scheduled submarine launches took place from the USS Tennessee (SSBN-734) on 21 March 1989. A malfunction during the first stage of powered flight caused the missile to veer off course, pinwheel, and self-destruct after 4 seconds of flight. On 23 March 1989 the Navy stated that the accident resulted from a mechanical or electrical malfunction in the area where the nozzle swivels to steer the missile.
As a result of the Navy's investigation, design modifications were made in first stage nozzles in the linkage area that transmits position commands to the nozzle. These design changes in addition to component delivery problems delayed deployment of the Trident II from late 1989 to March 1990.
The second launch marked the first underwater success for the Trident, but the third test on 15 August ended in failure, with the missile self-destructing 4 seconds into launch. The 2 failures were similar in that design flaws created the problem. As the missile was propelled to the surface, water was drawn into the nozzle of the missile, damaging the missile's steering system.
In mid-September 1989, the Navy said that modifications to the nozzles would be relatively inexpensive and would not delay the missile's IOC. The successful 4 December 1989 test of these modifications was briefly delayed by the ship GREENPEACE, but she was rammed by a US Navy ship (note: My ship, The U.S.S. Kittiwake, ASR-13 may she rust in peace) and her crew sprayed with fire hoses. The Navy continued with several more tests in December 1989 and completed its underwater test series in time to meet its planned IOC of March 1990.
You did good!