So over the last year, I've bought 3 bodies from AO, and 2 of them have incorrect o-rings for ULE bodies. They're simply too small, and the detents are going too far into the bodies, causing friction on the bolt. For the longest time, I couldn't understand why my balls were shooting inconsistent. Now I fixed it, but need to buy a couple of new detents. Guys, please check to make sure you have the correct o-rings on the detents!
They usually come with two o-rings. One is thicker than the other.
I also use blue loctite and mark the detent with nail polish or paint pen so I know where it is set.
With just the o-ring, mine would come loose and back out. Then I started checking that it was screwed in, and I worked it into the body too far. Now I just look at it to be sure it is where I left it.