HI! I'm an XR500 owner who has been been watching this topic for a while now and has gone through 3-4 firmware updates throughout the years. I have skipped the latest official update because it's just security fixes that are likely already included in the latest beta rc14.
Fraser, you've been extremely professional and knowledgeable. I know I can post a question and get a quick and informative response. But, in all honesty, you're the only good part about owning a Netgear router.
This DHCP issue has existed since I first purchased this router, and every firmware update makes it worse. My internet went from dropping out every roughly 2 weeks, to every 1-2 days, requiring intervention from me. Not a problem when it's at 3am when nobody is awake, it's just an inconvenience. However, it becomes a nightmare at 7pm when everyone is home using their devices and a baby starts crying because the only 10mins TV time they get all day is taken away.
I'm sure if you're a household with only a small handful of devices or no small children, it's possible that you'll never experience a problem or noticed one. But, I've been dealing with it fairly constantly for years.
So, for the last time, I've done a factory reset, 'upgraded' the firmware, and increase the DHCP range to begin at 100. The DHCP is still renewing leases every 1-2mins after six hours, which is an improvement over every 1-2 seconds and the DPI class still crashes and recovers every minute or two. So, it appears like something's still quite broken and the crashes will be inevitable.
I'll give it a week. Then I'm going to replace this XR500, contact Elon Musk, and have this cursed device fired into the sun where it cannot harm anyone else .