Ball joint issues

What model truck do you have? Can you post a photo of the control arm and of the pressing tool you are using? Have you compared the new ball joint to the old one?

In the meantime, check for burrs in the control arm. I have had more problems with the hole being wobbled out and the ball joint goes in too easily or even falls out. A lot of replacements even come with a giant snap ring, but a better and perfectly acceptable solution is to put a couple of small welds on it in an area easy to get to later to cut them when the ball joint needs to be replaced again. The snap ring is more of an insurance measure, but it will not keep the ball joint from wobbling the hole out even more.

The tool I use looks like a giant C-clamp with various cones and discs. There is a cone just the right diameter to sit on a flat flange on the joint. The joint cannot help but to go in straight, but I have run into problems of my own doing. The cone is pressed with a disc that sits in the C-clamp, and the proper disc for this purpose has a hole in the middle large enough for the ball joint's stud to peek through. I have had that stud get stuck under the disc, then the pressing force is applied to the stud rather than the joint's housing. That will destroy the threads on the end of the stud, and I have even gone so far as to push the ball through the plate in the bottom of the housing.