When a weld crack is found in service, immediately pull that cage out of the stacking area and take it out of use — a cracked cage still carrying load risks a stack collapse. After removing it, photograph the crack's location, length and any deformation, then report through the after-sales process; don't just tack a couple of weld beads on and keep using it.
Step two is to diagnose the cause. Use your phone to photograph the crack's starting point and path clearly, and send it to the maker together with this cage's usage record (stacking layers, loaded weight, whether overloaded). Cracks from manufacturing defects usually appear at post-to-base welds or at the root of stacking feet; cracks from overload or impact usually extend from the mesh panel where the blow landed.
Step three is the repair process: if the maker judges it a manufacturing defect, parts or a whole cage are replaced free; if judged misuse, the maker can offer a paid repair. A single small issue can be fixed by mailing spare parts and self-welding; batch cracking (over 5% of the same batch) should trigger an on-site investigation request.
Self-welding precautions: first grind both ends of the crack and drill stop-holes, then weld with a 3.2mm electrode and grind smooth, and afterward spray anti-rust paint. Never weld while the cage is still loaded, and don't just spot-weld as a temporary fix — strength recovered that way is less than half.
A repaired cage is best downgraded one level and no longer stacked to its original maximum height. Within the warranty period, Nanjing Tongnuo Warehouse Equipment Manufacturing Co., Ltd. provides free parts and technical guidance for weld defects caused in manufacturing, and can dispatch technicians on site for batch problems.