I feel the need to reply to this.. I've been buying/selling/riding Chinese stuff since around 2002. LITERALLY everything I've had has had this issue, and it's usually not the horrible MIG welds and I've seen it just with frame flex on paved road turns..
- People with big wallets have gone after Shenzhen makers and failed. Gov there protects them
- Importers and sellers are lucky to get spare parts let alone solve the problem of manufacturing
- I'm pretty sure sellers aren't liable, or have the budget to convince a judge so..
- It's Taiwanese recycled steel like the engine.. Have fun constantly MIG or TIG welding it(shielded oxy isn't even usable it'll ruining the frame).. I use high quality flux core and it usually just cracks next to your weld.. It's poorly refined on top of being high carbon