Yea , it does not make any sense to me either , how did the retainer clip look ?? , did it look like it had just failed/broke in half or all banged up ???, if it was not RPM related , then it could have been that the retainer clips were not seated properly when installed prior , maybe one side of it was , but the other maybe not and the only side holding it , could not take the load any longer and just decided to give way or it cocked sideways and then started cutting into the stem
The bend in the stem has me concerned about piston or rod bearing damage