Either the spring center bolt head is sheared off, u-bolts loose and or axle just installed wrong/not in the right place on the spring.
Or a simple mix-up that may not have been noticed at assembly is the springs are not the same end for end. The "center bolt" in the springs is not actually in the center, it's more to one end. With that understood one spring could be installed in the hangers the wrong way, doubling that offset and making the axle really crooked as you describe.
Grigg
