where do they keep breaking? and have you looked at the motor plate to see if its bent or cracked? theres got to be a reason for it to keep breaking motor mounts .. and i don't think jb weld will hold if its snapping aluminum itll snap jb weld.. theres got to be a visible reason for it to be breaking i would think... good luck hope you figure it out ..
Id almost have to say if you broke a cross member, though it may look straight that mill plate is toast too! Take it out and put it on a flat surface. Any part not touching the surface and it junk...