Looking at your second photo, the mount between both axles has a rubber insert called a shear spring that the shackles attached to. Yours is cracked but I can't tell how much. Cracks around a quarter inch deep are just normal aging of the sheer spring, but if you can put like a putty knife over 3/4 inch deep into them they need to be replaced. Here's an old post covering the subject.
https://www.montanaowners.com/forums...ad.php?t=48578