As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MAIN ACCOMPLISHED PREFLT INSP AND THEN PILOTS PROCEEDED TO DO THEIR PREFLT INSP. UPON NORMAL EXTENSION OF SPEED BRAKE PANELS, THEY RETRACTED WITH HIGH SPEED AS THOUGH SWITCHES WERE IN THE "GROUND AUTO DEPLOY" POSITION. DISASSEMBLLY OF RESTRICTOR VALVE SHOWED THAT IT HAD FAILED INTERNALLY EVIDENCED BY PARTIALLY CRUSHED MESH FILTERS AT EACH END AND SEPERATION OF RESTRICTOR FROM CENTER DEVIDER. THIS IS SECOND OCCURANCE ON THIS AIRCRAFT, M&D SUBMITTED AT FIRST OCCURANCE. SUSPECT THAT THIS ASSEMBLY IS NOT SUBSTANTIALLY STRONG ENOUGH TO WITHSTAND INTERNAL PRESSURES.