As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE START NORMAL. MAGNETO CHECK ON RUNUP REVEALED ROUGH RUNNING AND MAG CHECK FAILED ON SEVERAL CYLINDERS. REMOVED THE PLUGS - CRACKS FOUND ALL AROUND THE INSULATOR. RHB32S IS CURRENTLY IN THE ENGINE. HAVE BEEN FINDING SEVERAL OF THESE ON MULTIPLE AIRCRAFT - BOTH NA AND TURBO. THE ISSUE IS ISOLATED TO THE BRAND.