As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED HE HAD MAG DROP AT END OF LEG. OK AT RESTART AND AGAIN BAD AT ARRIVAL. RETURN LEG SHOWED HI-EGT AND HI-CHT. CHECKED MAGNETO TIMING FIRING AT TDC INSTEAD OF 20 DEGREES BDC. ATTEMPTED RE TIMING TO 20 DEGREES IN VAIN. CONCLUSION: INTERNAL WEAR AND SLIPPAGE.