As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT CRUISE, A SUDDEN ONSET OF A LOW AND STEADY VIBRATION WAS FELT THROUGH OUT THE AIRFRAME. NO OTHER ABNORMAL INDICATION WERE NOTED. ACFT LANDED WITHOUT INCIDENT. POST FLIGHT INSPECTION REVEALED THAT THE LT INBD AFT FLAP WAS MISSING A SECTION OF THE T/E. LT INBD AFT FLAP WAS R & R, OPS CHECKS GOOD. NO OTHER DEFECTS WERE NOTED. ACFT WAS RETURNED TO SERVICE.