On February 21, 2018, about 1015 Pacific standard time, an experimental, amateur-built G-2 airplane N90SR, sustained substantial damage when it was involved in an accident near Elko, Nevada. The pilot sustained serious injuries. The airplane was operated as a 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, upon landing, the airplane's left brake was inoperative, and he chose to conduct a go-around and set up for a single-brake landing. The subsequent landing was uneventful; however, the left brake was still inoperative. The pilot reported that, with about 1,500 ft of runway, he chose to veer to the right off the runway surface to avoid running off the end. Subsequently, the airplane struck a drainage ditch berm. The wheel brake system was hydraulically driven, and each brake operated independently from the front or rear cockpit and from the right or left side. A hydraulic fluid reservoir was located in the front cockpit, and its quantity was indicated in a fluid quantity window. Examination of the airplane revealed that the fuselage had sustained substantial damage and that the nose and left main landing gear struts had separated from the airplane. When the right brake pedal was depressed, continuity to the right brake was established; however, when the left brake pedal was depressed, hydraulic fluid moved through the brake lines and expelled from a severed portion of the lines under the left wing. The hydraulic fluid reservoir located on the front cockpit’s left side contained a normal quantity of fluid, and the fluid quantity window indicated between the maximum and minimum level. No hydraulic fluid leaks were noted in the cockpit area or on the interior or exterior of the left wing. Hydraulic fluid was noted on the left main landing wheel area. The fluid was clear and red and appeared to be fresh. Additionally, three separated brake pucks were found in the left wheel area. Examination of the left brake assembly revealed that the separated ends of the hydraulic lines were still secured and appropriately safety wired. Two brake rotors were found loose, and the No. 2 brake cylinder worn pin indicator was recessed. The other three brake cylinders’ wear pins were found in the normal position. Disassembly of the No. 2 brake cylinder revealed that it was not properly installed, which allowed the brake pucks to move. The movement of the brake pucks resulted in three of them separating from the brake assembly. The separation of the brake pucks could result in the No. 2 cylinder's piston being moved to the full-scale, inward position. Subsequently, the full-scale deflection of the No. 2 cylinder's piston could result in a hydraulic leak and cause insufficient hydraulic pressure to be provided to the other brake cylinders, rendering the brake inoperative. According to the airport manager’s report and a review of photographs of the accident site, during the landing, the airplane exited the runway with about 1,675 ft of runway remaining.