Yeah the 1020's were terrible for cracking the frame there. Our 30ft did it took. Couldn't figure out why halfway through soybeans everything was vibrating so badly. Til we got done and got the head cleaned up and started looking at it closer.
had same problem last year. welded it back at least twice. finally figured out the bushings that hold the arm which wobblebox attaches to the head were wore out causing some left to right movement everytime the sickle took a stroke putting a lot of stress on backer bar. Replaced bushings and fixed problem.