At the best of times, injection moulded plastic is not a substitute for metal alloy if you want it to last. That you had a failure right out of the box shows that, in this case, some accountant somewhere has shaved a bit too much off of the cost of raw materials and ended up ruining a good product before it even gets to the end user. Why use sub-standard parts? Because it's a bl**dy rip-off, that's why.
Furthermore - Any manufacturer who puts chrome plated plastic parts into an assembly looses all chances of further business from me. Those nasty control knobs, like on my Laney RB3, are an example. Once bitten forever shy.
/rant.