Automatic when I don't want it

[hswaters]

I have a Craftsman 12" lathe that I got sometime in the early 70's. It is ok for most things but since I cleaned it up and replaced the half nuts. Now just a little vibration and the half nuts close and we are off to the races. And it happens when I least expect it which means I often get cuts I don't want. Both half nuts have a hole for the little ball to park in. The last time I took it apart I turned the frame the half nuts are in 180 degrees so the other half nut hole would be lined up with the ball. It seemed like it was fixed for a short time, mainly a few minutes then it took off again. When the old half nuts were in there was no lubricant on the half nuts, mostly crud and corrosion, and they were very stiff and this problem never came up. Does anyone have a similar lathe? Maybe some suggestions? I may just clean out all of the grease and get them stiff again if possible.