I'd return it if I were you. I bought one for my mum and it works fine. Was using it this afternoon and the nozzle retracts fully and the lip doesn't bend up in the middle. Vacuuming was fine, so I'd guess you may have a dodgy one?
When I took a look at it, I realised that it's slightly different to mine. My guess is same internals, but slightly different build quality as you pointed out. The locking mechanism is different (mine has clips while yours doesn't) which doesn't seem as rugged, but overall I thought it was pretty good.
Contact the ebay seller and let him know what the issues are.