...I googled up your bike, and it appears the original tires are Schwalbe Super Moto x2, so pretty OK tires.
500 miles doesn't sound like a lot of wear, and given your description of your flat history (500 miles fine, then a series of repeats), it wouldn't surprise me if maybe there is something in the tire, or the rim strip, that is sitting in the tire, and causing the repeats. I do not know how sophisticated you are at this, but whenever you repair a flatted tube, you need to find the source of the injury. There are things like tiny bits of wire that are shed by steel belted radial car tires on the road. They get in the tire, work their way in just deep enough to occasionally poke at the tube, and will cause a repeat flatting issue. Likewise, sometimes there are fine metal shavings from drilling the rim, that get stuck in the rim tape, and do the same thing.
The best way to find such things is to very carefully mark the leaking spot on the tube, and match it against the tire and rim for location, These things can be difficult to find, and you need to pull them out with some sort of pliers or a surgical hemostat.
Sorry, that's al I got. I have thrown away at least one or two tires that repeat flatted, just because I couldn't fine the problem in the tire. It was just cheaper and easier to buy a new tire, after three flats.