They were only $70.00 new, so not a lot you can do to fix them that is worth the cost.
A Jennings J22 was my very first gun, I would probably never buy another, but I will not get rid of the one I have since it has sentimental value. However I would like to find a replacement top slide for mine since mine developed a crack in it after about 12 to 15 Thousand rounds.
The only problem I ever had with it was when I first got it, it would not eject about 25% of the time, I had to use a file and deepen the area where the ejector would hook over the rim of the case and that fixed it.
One other thing that I did not know about till years later that may have helped lead to the slide cracking was you are not supposed to use any of the super high velocity ammo such as Yellow Jackets and other I can not think of the names of right now.
Michael Grace