Yes on this style the bodies are meant to be pressed into a drill hole in the casting. And that's the issue on some of the Asian machines & tools where this drilling operation is so-so. The drill hole can be +/- and also probably the bodies can be +/- so the range of fit can vary. If you have a tight or distorted hole & tap them in with too much force, the thin brass can distort up in the ball area or around the skirt crimp area. If the ball get stuck in open position then oil can weep out if there is a little bit of back pressure. I think the light spring force is just to keep the ball somewhat seated so debris doesn't get in there.
If you had a loose fit hole, probably could use a drop of sealant or blue Loctite. I've seen them drilled from the top & pull shrapnel with needle nose pliers (Stefan video, his rotary table episode maybe?)