Either the rods are warped or the frame is warped, or both. On one side, the rod would come out of the track as I passed the carriage over the joint. I fiddled around with it on Sunday and thought I had it fixed. It seemed to be ok when I was practicing and I made this short video. I had to hold the camera with one hand. Believe me, I prefer to use two hands and I can see that I get better results.
Update. Steven held the camera and I quilted.