For example: my router/AP/modem combo-box — which is the standard one that Comcast has been giving to all subscribers — when reset or power cycled, will forget the WiFi key. It just gets reset to the factory default. Every, single, time. And it's just they key: the SSID doesn't get reset. It's not the first modem I've had, either; its predecessor was the same make, had the exact same behavior.

I suspect it's because I'm using an actual key, instead of a passphrase, and nobody else does that. (Or, at least, not enough for Comcast to notice that the problem is them.)

The old one got returned b/c it was routinely dropping IPv6 packets. It took a while — multiple vists from multiple technicians — to convince Comcast that the symptom of "100% packet loss over IPv6, 0% packet loss over IPv4" was not a problem with the coax cable.

The predecessor of that modem got replaced when it had extreme difficulty forming IPv4 connections: almost all SYNs never got a SYN ACK, but in the rare case that they did, that connection proceeded with 0% packet loss. I highly suspect there was something going horridly wrong with its NAT processing, but that's a guess.

The worst is that the Linux kernel (and any BSD) would be able to make a perfect router, but manufacturers insist on using their own shitty implementation. If they would've just used used the default Linux/BSD they would've been fine.