On June 26, 2020, about 2100 central daylight time, a Piper PA28R-201, N811MS, was substantially damaged when it was involved in an accident at Rocky Mountain Metropolitan Airport (BJC), Broomfield, Colorado. One passenger sustained minor injuries, and the private pilot and two passengers were not injured. The airplane was operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. The pilot departed BJC, flew to a nearby airport, and was returning to BJC when the accident occurred. He reported that his shoulder harness inertial reel locked up while preparing for the outbound and return flights for no apparent reason, but he was able to free up the harness in both cases. The pilot reported that he arrived back at BJC with about 15 gallons of fuel left in the airplane (10 gallons in the right tank and 5 gallons in the left tank). The pilot requested clearance to perform a touch-and-go maneuver at BJC. Shortly before the turn from base to final, the pilot’s shoulder harness locked up once again. He leaned back to release the belt, but it took out the slack without releasing. After touchdown, the pilot performed the touch-and-go, with the shoulder harness still locked. During the climb, the engine hesitated and the pilot pitched the airplane forward. Suspecting a fuel issue, the pilot attempted to switch fuel tanks. The pilot stated that it was difficult to reach the fuel selector lever because of the shoulder harness not releasing. The pilot abandoned further attempts to switch fuel tanks and initiated a left turn toward flat terrain for a forced landing. The airplane landed in a field about 350-feet beyond the departure end of runway. The airplane came to rest upright adjacent to a tree line, resulting in substantial damage to the left wing. A postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. The fuel distribution system was intact and appeared normal. Cockpit throttle and mixture controls were rigged properly and appeared normal. The cockpit fuel selector valve was found in the left tank position. A total of about 4.25 gallons of fuel was removed from the left and right fuel tanks; 4 gallons from the left tank, and .25 gallons from the right tank. The tanks were not compromised. The cockpit fuel gauges appeared to function normally When examined, the pilot’s inertial reel on the shoulder harness did not function properly as the pilot reported. The airplane flight manual states that the unusable fuel for the airplane is 5 total gallons, 2.5 gallons in each fuel tank for critical flight conditions.