As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MGB OIL FILTER CHANGE, FOUND O-RING IN WRONG GROOVE ON OIL CLOGGING INDICATOR FOR THE LOWER END OF FILTER. THERE ARE TWO GROOVES BUT ONE IS JUST PART OF THE DESIGN OF THE HOUSING AND IF O-RING IS IN THIS WRONG GROOVE, UNFILTERED OIL CAN BYPASS THE FILTER AND CAUSE CONTAMINATION TO SPREAD THROUGHOUT OIL SYSTEM.