Ryobi and Makro - poor service twins

Ryobi Generators - service life of 4 months. I bought a 7,5kva Ryobi generator from Makro Online. It worked ok for 4 months. By 'ok' I mean it struggled to power 2 fridges, a few globes, router, dstv and TV. After 4 months the AVR system failed and it pushed >320V into my house, causing obvious damage. Makro refuse to honour their warrantees and Ryobi want me to pay for repair to their faulty/defective generator.