I would echo the above comments. There are just far too many unscrupulous companies in China making and selling crap via eBay. Amazon, Aliexpress etc. Bear in mind that this box controls mains power to your car. Do you really want an unseen defect in there putting full mains voltage on the car body, that anyone could touch and get a shock?
If anyone thinks this doesn't happen, then I have personal experience that suggests it does. I bought a load of Chinese made LED downlights, installed them all, and they worked just fine. I was curious as to how hot they were getting when on, so touched one and got a belt. After investigation I concluded that, because of the design, there was a 50:50 chance that a metal ring around the front face would be live. These were sold by a reputable UK big-name store, that had been deceived by the manufacturer faking the safety approval marks and documentation
As for an eBay example, I bought a "smart" battery charger some years ago, from a Chinese vendor on eBay. I was a bit suspicious when it arrived, as it had a metal case, yet only a two core cable, which was clearly wrong (two core implied that the thing was Class II, and the metal case suggested that was not likely). I decided to check it, and discovered that the mains cable colours had been swapped around inside, so the blue was connected to the internal fuse and the brown was connected to the battery negative terminal, believe it or not. Not only was there no isolation, but the line input, at 230 VAC, was directly connected to the croc clip on the battery negative lead. Had I plugged it in, then it would have made the battery negative terminal, and anything connected to it, live.
This is far from being unusual for Chinese made stuff sold on eBay, Aliexpress, Amazon, etc, a fair bit of it is very often bordering on being lethal. A look at BigClivedotcom's YouTube channel can be educational, and show just how much potentially lethal tat gets sold on these sites, almost all of it coming from that part of the world.