если кому интересно, пришел ответ от stuart turner uk(писал им чтобы дали пояснения) : Thank you for your email regarding the shaft failure on your Stuart Turner pump, model 44934, and for providing the background to the issue.
We have now completed our investigation into the failed shaft.
The motor shaft is specified to be manufactured from stainless steel grade 1.4401 (316). Analysis of the returned shaft confirmed that it was stainless steel; however, the material composition did not fully conform to the specified 1.4401 grade.
While this material variation was identified during our investigation, we are unable to confirm that it was the sole or direct cause of the shaft failure, and nothing in this response should be taken as an admission of liability.
Further testing has confirmed that shafts currently being supplied meet the specified 1.4401 stainless steel requirement. Additional material verification controls have also been implemented by the supplier as part of our ongoing quality assurance processes.
We have also considered your concern regarding the authenticity of the pump. There is no indication from our investigation that the pump was counterfeit or an unauthorised product.
Thank you for bringing the matter to our attention and for allowing us the opportunity to investigate.

кратко:насос оригинальный, вал должен быть из 316 нержавейки, а был из говна и палок. но у нас все ок, все проверяется, ни за что не отвечаем.

насос поменяли по гарантии тут на Кипре(еще до письма на завод). но я уже успел купить другой такой же. меня интересовало другое, они все такие теперь, или это у меня был поддельный/ремонтный/бракованный. их ответ тоже странный, на фото четко видно внешнее кольцо из нержавейки, а не сам вал целиком из нее