As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - FLT 587 - APU GENERATOR WENT OFF-LINE AND WOULD NOT RESET. FAILURE ACCOMPANIED BY ELECTRICAL SMELL WHEN APU AIR IS USED. INSPECTED APU, OIL LEVELS OK. INSPECTED MAG PLUG AND FILTERS, NO CONTAMINATION NOTED. STARTED APU, APU GEN OPS NORMALLY UNDER LOAD. NO ELECTRICAL SMELLS NOTED.