Peter
"Reliable" is a very broad church. Industrial running every day at close to rated capacity is hugely different to occasional home shop use on a lightly loaded machine. Home shop types pretty much never approach the real metal shifting capacity of a machine, especially not industrial capable varieties, simply because dealing with large quantities of chips at high velocity is such a major league pain.
Issue with E-Bay import, whether "no brand" or "who they" brand, is that you don't know the standards of manufacture. Worse the E-Bay supplier generally doesn't either. Technical back up being essentially non-existent too. At best the inexpensive ones are devices from third or fourth tier makers. At worst a bunch of "surplus" standard line parts, which may well work but be below specified performance, assembled by outworkers in their back rooms. Things from the bottom end of the supply line probably haven't been turned on, let alone tested, before boxing up for dispatch. Which is worrying.
These days it can probably be assumed that the semi-conductor side of things is at least adequate, however marginally. So magic smoke release soon after purchase is rare. Although I'd be chary at running "no name" at its full rated capacity. The PCB boards on cheap import won't be up to industrial standards but should be good enough for the job. Probably unwise to let the shop get damp tho'.
For me the big issues would be the quality of the capacitors feeding the DC bus, how effective the safety components are, how good the control software is and whether or not the control software has actually loaded properly. Inverters are notoriously hard on their capacitors which are a consumable item needing periodic replacement after sufficient operating hours. For good quality ones probably more hours than home shop use will rack up. But first quality ones are expensive. Almost certainly the place where a lower end maker will shave quality. In practice probably fine unless they shave too far.
Fundamentally you just don't know for sure what you are getting. Something from a decent third or fourth tier maker ought to be more than good enough for home shop guy but at the back end of an E-Bay supply chain finding out what you actually have is hard. Heck some of the third and fourth tier brands have been knocked off by the build in a back room crowd. Just because the one Jack got at super bargain prices last year is still running fine it doesn't follow that the one you get will still be good. Jack might have been lucky, or hardly uses it, or its only on light duties or ….
Personally I can't be bothered with the risk. For me the objective real £sd difference in price between "has a good chance of being just fine" purchase off E-Bay and the real thing from Inverter Drive Supermarket or a similar supplier isn't worth the potential issues.
Your mileage, and depth of pocket may differ. Mine certainly would have done 40 odd years back when every £ really ought to have done the work of 5, or even 10 if I could manage it. These days I'm a bit more affluent and, at 65, have to seriously factor in how many good years I have left and what I want to spend them doing! Paying a bit more for "just works like it says on the tin" is attractive.
Clive