Why do my edge prints always fail while the centre ones come out fine?

That pattern, all four corners bad and the middle clean, points away from leveling. A tilted plate messes with one side or one edge, not a clean symmetric ring around the center. I chased the same ghost on mine and it turned out to be light falloff at the edges. The light is brightest in the middle of the screen and drops off toward the corners, and as the screen and LED panel age that falloff gets worse. So the center keeps getting plenty of cure while the corners slip just under what fine details and thin supports need. That fits your symptoms exactly: bottom layers stick everywhere becuase they get a much longer cure, then once you're into normal layers the corner details are running on marginal exposure and start tearing off.

Easy way to confirm it. Run your test model again but only in the four corner spots, with normal exposure bumped up a tenth or two of a second. If the corners come good and the middle starts looking a touch overcured, you've found your answer. You can also do a small exposure ladder in a single corner position and compare where the corner starts passing versus where the center does. If there's a real gap between them, that's your light non-uniformity showing itself. Film tension wouldn't usally give you a neat symmetrical pattern like this either. A loose film causes random inconsistent failures all over, and a scuffed or cloudy patch causes failures right where the damage is. Still worth pulling it out and holding it up to a light since it takes two minutes, expecially if it's got a lot of prints on it, but I wouldn't put money on it being the cause here.

If a small bump in exposure sorts the corners out, you can just run that and accept the center being slightly overcured. On my machine the difference was small enugh that everything printed fine across the whole plate with the bumped setting.

Same story here on my old Mars. I bumped exposure and the corners got better but never fully matched the middle, and I kept second-guessing myself untill I grabbed a cheap little UV meter card off the usual shopping site. Pressing it against the screen in the center vs the corners showed the gap plain as day, way bigger than I expected on a machine that was barely a year old. Took all the guesswork out of dialing a compromise exposure. Might be overkill if the exposure bump alone works for you, but if the corners keep chewing supports even after that, that little card will tell you in two minutes wether the light itself is the problem.

I'd push back on the aging light source theory in the first reply. The OP literally said this is a new printer. Light falloff from a worn screen or dimming LEDs takes a long time to show up, it doesn't hit like this within the first handful of prints. If the uniformity was bad enough to chew supports out of the box, that's a warranty issue, not a tune-it-with-exposure issue. My money would be on plate flex instead. Overtightening the screws can actually bow the plate slightly, which is why it feels tight but still prints wrong at the ends. When you re-level, snug it down on the film with the screwdriver held lightly, not cranked. If corners still fail after that, then sure, run the exposure ladder and see what it tells you.

Total newcomer here so take this with a grain of salt, but I had something sort of similar on my little printer and it turned out to be temprature. My setup is in the garage and the resin near the edges of the vat was colder than the middle, probaly from a draft, and thin supports in those areas just fell apart until I warmed the room up. Probably not your issue since yours sounds indoor and consistent, but cold resin does weird stuff to small features so figured I'd throw it out there. Also, following the third reply's point, if it is a uniformity problem on a brand new machine I'd definitely be contacting the seller rather than tweaking settings around it.

Before you blame the light source, do the pedantic thing and put a straightedge across the plate itself. Mine had a slight dish to it, high in the middle, so the corners got squished harder during levelling and the first layers there were a hair thicker, wich only showed up once the print got tall and the stress added up. The fact that your corners fail as a matched set is actualy consistent with a dished or crowned plate, not against it. Also worth remembering that the corner positions sit close to the vat walls, where the resin does not flow back in as easily after each peel, so if your wait between layers is on the short side the corners cure in slightly starved resin.