As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AT FL200 FUMES IN THE COCKPIT AND REAR AREA OF THE AIRCRAFT. SMELL WAS WET SOCKS AND REMAINED FOR THE REMAINDER OF FLIGHT. REMOVED AND REPLACED O-RINGS COMMON TO THE APU FAN ASSY IAW AMM 49-52-51. REF J/C 26L00021001, 26L00021002, 26L00021004.