The pin can wear through the threaded bushing into the shackle mount. It usually happens on one side of the shackle and winds up looking like yours does. A replacement of the bushing and pin usually repairs that, unless the shackle mount is severely worn. If there's not enough metal in the mount to hold the new bushing tightly, it could be welded and remachined to the right diameter, but that's a pretty severe fix.
You need to disassemble the shackles and remove the pins to check them out.
