There is a particular flavour of regret reserved for the moment a working router goes dark on the bench. I know it well, because I went back for seconds.
The first flash had failed quietly: it booted, but the radio was deaf, the 5GHz band simply not there. A driver mismatch, almost certainly, the kind of thing where the firmware build and the actual chip revision disagree about which calibration data lives where. I should have reverted and walked away. Instead I convinced myself a different image would fix it, and flashed again.
The second flash bricked it outright. No console output beyond a checksum failure, the bootloader sulking. I spent an evening on TFTP recovery, feeding it the stock image byte by byte over serial until it came back to life as the boring vendor firmware it had started as.
The honest conclusion is that this particular board and this particular custom firmware were never going to get along, and that no amount of stubbornness on my part was going to change the silicon. Sometimes the win condition is restoring the stock image, admitting defeat, and ordering a model that's actually on the supported hardware list. The router lives on as the spare it always wanted to be.