That is not impossible - the CH340G serial adapters you get on ebay for $1 each, while they usually work, are... still $1 serial adapters (and the ones you get elsewhere for more are typically the same ones, just with a higher price). The build quality is often shoddy - I have seen ones where the USB connector wasn't completely soldered on.
I normally use the black ones with the voltage switch (the black ones that don't have the voltage switch are trash - they don't break out DTR, and are the ones where I saw the USB connector not soldered down properly), or the green ones with the micro USB connector and voltage switch. The green ones are probably my favorite (a bit harder to find, but they are there on ebay), since everyone has buckets of micro usb cables, while full sized usb extension cables are somewhat uncommon. The term i search ebay for to find CH340G adapters is "ch340g 6pin" (without the quotes). And yes, this being direct-from-china-ebay-land, your best bet to identify what you're buying is the pictures.