Thanks Dave for material.
the lubrication is just follow the manufacturer and no any abnormal. The spec for oil is VG100, The oil was maintaining and changing as manufacturer then i have no doubt in oil issue.
As see the defect mark, look like a very excessive load effect on gear and broken the teeth surface, the spectrum also shows high GMF relate to gear wear , also indicates very high load.
then the next question is why the high load on the gear , i keep going my investigation on this way/...