I know that if you don't clean the oil out of the bolt holes, it can get tight and to the torque limit. Then as the oil seeps up through the threads, it will get loose.
I always make sure to spray the holes out with an air hole. Then pour in a little alcohol, clean with a Q-tip, and spray out again. This makes sure the bolt holes are clean and I get a good torque reading and the bolts don't come loose over time.