The router was fine. That is the part I want on record. It routed packets, it did not fall over, the family could watch their things without me being summoned. There was no problem to solve. So naturally I flashed it.
The excuse was OpenWrt. I wanted proper VLANs and a config I could keep in git rather than a vendor web UI that forgets settings on a whim. All reasonable, all things I did not strictly need that evening. The flash itself went smoothly, which is exactly when you should get nervous.
It came up, took my config, then bricked itself the moment I touched the switch settings and rebooted. No lights, no ping, no web interface. Dead, on my desk, on a Saturday night.
What saved me was TFTP recovery and the failsafe mode that most of these devices hide behind a held reset button during the first few seconds of boot. I had to read the wiki page properly, which I had skimmed earlier with the confidence of a man who would not need it. Twenty minutes and one cautious re-flash later it was back.
It is working now, with VLANs, and the config is in git. Was it worth it? The honest answer is that I would have been happier if I had left it alone, but I learned exactly where the recovery rope is hidden, and one day I will be glad I pulled it once on purpose.