I thought so too. Its definitely a snug fit. Its snug enough to where if I turned the frame upside down and shook it violently the cup still wouldnt fall out. But I can definitely pull it out by hand with a little effort. I'll try loc-tite I guess. Thanks for the suggestion.
I'll probably just buy a new upper cup before trying out a knurling tool and if the new cup has the same problem, its probably the frame and I'll go with the knurling tool.
Is it also odd that the lower cup went about 3/4s of the way in before beginning to resist? The few other times I've pressed in cups, they wont go in but a millimeter or two before requiring the press, suggesting that the tolerances were pretty exact. I was almost able to press these in by hand. Thanks for the help.